# Air Plan Revisions; California; Heavy-Duty Vehicle Inspection and Maintenance Program > Briefs, arguments, decisions, and more. URL: https://www.frixlaw.com/law-library/documents/fr%3A2026-02350 ## Record - **Collection:** Federal Register - **Document type:** Rule - **Published:** February 6, 2026 - **Citation:** 91 FR 5325 ## Text ENVIRONMENTAL PROTECTION AGENCY 40 CFR Part 52 [EPA-R09-OAR-2025-0061; FRL-12606-02-R9] Air Plan Revisions; California; Heavy-Duty Vehicle Inspection and Maintenance Program AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: The U.S. Environmental Protection Agency (EPA) is taking final action to partially approve and partially disapprove a submission by the State of California to revise its State Implementation Plan (SIP) relating to the control of emissions from non-gasoline combustion vehicles over 14,000 pounds. The EPA's partial approval will allow the submitted Heavy-Duty Inspection and Maintenance Regulation (“HD I/M Regulation”) to become federally enforceable as part of the California SIP with respect to vehicles registered within the State. The EPA is partially disapproving the submission to the extent that the HD I/M Regulation purports to apply to out-of-state vehicles as inconsistent with the Clean Air Act (CAA), because the State has not provided adequate assurances under CAA section 110(a)(2)(E)(i) that implementation of the SIP is not prohibited by Federal law. The partial disapproval will not trigger CAA section 179 sanctions because the submittal is not a required submission under CAA section 110(a)(2). DATES: This rule is effective March 9, 2026. ADDRESSES: The EPA has established a docket for this action under Docket ID No. EPA-R09-OAR-2025-0061. All documents in the docket are listed on the https://www.regulations.gov website. Although listed in the index, some information is not publicly available, e.g., Confidential Business Information (CBI) or other information whose disclosure is restricted by statute. Certain other material, such as copyrighted material, is not placed on the internet and will be publicly available only in hard copy form. Publicly available docket materials are available through https://www.regulations.gov, or please contact the person identified in the FOR FURTHER INFORMATION CONTACT section for additional availability information. If you need assistance in a language other than English or if you are a person with a disability who needs a reasonable accommodation at no cost to you, please contact the person identified in the FOR FURTHER INFORMATION CONTACT section. FOR FURTHER INFORMATION CONTACT: Doris Lo, EPA Region IX, 75 Hawthorne St., San Francisco, CA 94105; telephone number: (415) 972-3959; email address: lo.doris@epa.gov. SUPPLEMENTARY INFORMATION: Throughout this document, the use of “Agency,” “we,” “us,” or “our” refers to the EPA. We use multiple acronyms and terms in this preamble. While this list may not be exhaustive, to ease the reading of this preamble and for reference purposes, the EPA defines the following terms and acronyms here: ACT—Advanced Clean Trucks ATA—American Trucking Associations CAA—Clean Air Act CAELP—Center for Applied Environmental Law and Policy, Environmental Defense Fund, and Natural Resources Defense Council CARB—California Air Resources Board CBI—Confidential Business Information CCA—Coalition for Clean Air CCAEJ—Center for Community Action and Environmental Justice and Sierra Club CCR—California Code of Regulations CFR—Code of Federal Regulations CRA—Congressional Review Act CTA—California Trucking Association EPA—Environmental Protection Agency FIP—Federal Implementation Plan FSOR—Final Statement of Reasons GVWR—Gross Vehicle Weight Rating HD I/M—Heavy-Duty Inspection and Maintenance HDVIP—Heavy-Duty Vehicle Inspection Program ISOR—Initial Statement of Reasons MECA—Manufacturers of Emission Controls Association NTTAA—National Technology Transfer and Advancement Act NTTC—National Tank Truck Carriers OBD Standards—California Standards for Heavy-Duty Remote On-Board Diagnostic Devices OMB—Office of Management and Budget OOIDA—Owner-Operator Independent Drivers Association PRA—Paperwork Reduction Act PSIP—Periodic Smoke Inspection Program RFA—Regulatory Flexibility Act RFP—Reasonable Further Progress SCAQMD—South Coast Air Quality Management District SIP—State Implementation Plan TRALA—Truck Rental and Leasing Association UCS—Union of Concerned Scientists UMRA—Unfunded Mandates Reform Act U.S.C.—United States Code USMCA—United States-Mexico-Canada Agreement Table of Contents I. Background A. CAA Requirements B. What regulations did the State submit? C. What is the purpose of the submitted regulations? D. What did the EPA propose? II. The EPA's Evaluation and Final Action III. Response to Public Comments and Discussion A. Comments in Support of Partial Disapproval B. Comments in Support of Full Approval C. Other Comments IV. Incorporation by Reference V. Statutory and Executive Order Reviews I. Background A. CAA Requirements Under the CAA, the EPA establishes national ambient air quality standards (NAAQS) to protect public health and welfare. The EPA has established NAAQS for certain pervasive air pollutants including ozone, carbon monoxide, nitrogen dioxide, sulfur dioxide, lead, and particulate matter. Under CAA section 110(a)(1), States must submit plans that provide for the implementation, maintenance, and enforcement of the NAAQS within each State. Such plans are referred to as SIPs, and revisions to those plans are referred to as “SIP revisions.” CAA section 110(a)(2) sets forth the content requirements for SIPs. Among the various requirements, SIPs must include enforceable emissions limitations and other control measures, means, or techniques as may be necessary or appropriate to meet the applicable requirements of the CAA. 1 SIP revisions may be submitted to address specific CAA requirements (such as the elements and demonstrations required within an attainment plan), or, as with the State submittal addressed in this action, may be provided to demonstrate emissions reductions to support attainment. 1 See CAA section 110(a)(2)(A). Upon receiving a SIP that meets the completeness criteria in CAA section 110(k)(1)(A), the EPA must determine whether the submission meets all applicable CAA requirements. 2 The EPA must either approve, conditionally approve, approve in part and disapprove in part, or disapprove a complete State submission within twelve months. 3 In addition to the limitations described above, CAA section 110(a)(2)(E) provides that a SIP must include “necessary assurances” that the State “is not prohibited by any Federal or State law from carrying out such implementation plan or portion thereof” and that the State or applicable State entity has adequate authority, personnel, and funding to carry out adequate implementation of the SIP. 2 See CAA section 110(k)(3). 3 Id.; CAA section 110(k)(4). Under California law, the California Air Resources Board (CARB) is the State agency responsible for adopting and submitting SIP revisions to the EPA for review. These include both local rules adopted by county and regional air districts (typically regulating stationary source emissions) and statewide regulations adopted by CARB and other State agencies. If approved into the SIP, submitted regulations become federally enforceable pursuant to CAA section 110(a)(2)(A). B. What regulations did the State submit? CARB submitted the “Heavy-Duty Inspection and Maintenance Regulation” 4 (“HD I/M Regulation”) as a revision to the California SIP on December 14, 2022. 5 Table 1 identifies the regulatory sections included in the HD I/M Regulation and addressed by this action with the dates that they were adopted by CARB and submitted to the EPA. 4 The State of California more commonly refers to the HD I/M Regulation as the “Clean Truck Check.” See, e.g., CARB, Clean Truck Check (HD I/M), https://ww2.arb.ca.gov/our-work/programs/CTC (last visited January 26, 2026). 5 Letter (with enclosures) dated December 7, 2022, from Steven S. Cliff, Ph.D., Executive Officer, CARB, to Martha Guzman, Regional Administrator, EPA Region IX (submitted electronically December 14, 2022). The letter and enclosures, which include the HD I/M Regulation, among other materials, are included in the docket for this rulemaking. Table 1—Submitted Regulations Agency Regulation title Relevant sections of California Code of Regulations (CCR) Adopted Submitted CARB Heavy-Duty Vehicle Inspection and Maintenance Program Amended section: 13 CCR 2193; New sections: 13 CCR 2195, 2195.1, 2196, 2196.1, 2196.2, 2196.3, 2196.4, 2196.5, 2196.6, 2196.7, 2196.8, 2197, 2197.1, 2197.2, 2197.3, 2198, 2198.1, 2198.2, 2199, and 2199.1 12/09/2021 12/14/2022 The HD I/M Regulation incorporates by reference the “California Standards for Heavy-Duty Remote On-Board Diagnostic Devices” (“OBD Standards”). CARB approved the HD I/M Regulation on December 9, 2021, through Resolution 21-29. Following minor, non-substantive edits by CARB staff, 6 CARB formally adopted the final HD I/M Regulation and OBD Standards on August 22, 2022, through CARB Executive Order R-22-002. For more information on the HD I/M Regulation, including the EPA's prior actions on precursor SIP submittals, see section II of the preamble to the proposed action. 7 6 CARB, Addendum to the Final Statement of Reasons for Rulemaking, “Public Hearing to Consider Proposed Heavy-Duty Inspection and Maintenance Regulation” (October 4, 2022). 7 90 FR 41525, 41528 (August 26, 2025). C. What is the purpose of the submitted regulations? Based on ambient data collected at numerous sites throughout the State, the EPA designated certain areas within California as nonattainment for the ozone NAAQS and the particulate matter (PM) NAAQS, which includes both coarse and fine particulate matter ( i.e., PM 10 and PM 2.5 ). 8 The EPA redesignated to attainment several areas in California previously designated as nonattainment for the carbon monoxide NAAQS because these areas attained the standard and are subject to an approved maintenance plan demonstrating how the State will maintain the carbon monoxide standard into the future. 8 See generally 40 CFR 81.305. Mobile source emissions constitute a large portion of overall emissions of ozone precursors, including volatile organic compounds (VOC) and oxides of nitrogen (NO X ), as well as direct PM and PM precursors, including NO X , sulfur dioxide (SO 2 ), and carbon monoxide in the various air quality planning areas within California. 9 According to CARB, heavy-duty vehicles constitute 52 percent of the on-road NO X emissions and 54 percent of on-road PM 2.5 emissions. 10 In addition, according to CARB, out-of-state or out-of-country heavy-duty vehicles constitute approximately half of the total number of heavy-duty vehicles travelling in the State and approximately 30 percent of heavy-duty vehicle NO X emissions. 11 According to CARB, the HD I/M Regulation is intended to reduce PM 2.5 and NO X emissions from heavy-duty non-gasoline combustion vehicles operating in California to further ozone and PM attainment by areas within the State. 12 9 VOC and NO X are precursors responsible for the formation of ozone, and NO X and SO 2 are precursors for PM 2.5 . SO 2 belongs to a family of compounds referred to as sulfur oxides. PM 2.5 precursors also include VOC and ammonia. See 40 CFR 51.1000. 10 See “Public Hearing to Consider the Proposed Heavy-Duty Inspection and Maintenance Regulation—Staff Report: Initial Statement of Reasons,” October 8, 2021, at I-2 (“Staff Report”). 11 Id. at II-2. 12 Id. at II-1. The HD I/M Regulation establishes a comprehensive I/M program for heavy-duty vehicles that is intended to ensure that vehicle emissions control systems on these vehicles are operating as designed and repaired quickly. CARB asserted that this regulatory revision builds on CARB's current heavy-duty inspection programs, including building on and replacing the Heavy-Duty Vehicle Inspection Program and Periodic Smoke Inspection regulations for heavy-duty vehicles. 13 13 13 CCR 2180 through 2189. These programs are sunset under 13 CCR 2199.1, which is included in the HD I/M Regulation SIP submittal. The HD I/M Regulation applies to all non-gasoline combustion vehicles above 14,000 gross vehicle weight rating (GVWR) that operate in California. Unlike virtually all prior CARB regulations and similar regulations adopted by other States, the HD I/M Regulation would also apply to vehicles registered out-of-state and out-of-country that operate within the State of California for almost any length of time. 14 Some vehicle categories are exempted, including zero-emission vehicles ( i.e., electric vehicles), emergency and military tactical vehicles, and other classes defined by use or purpose. There is a limited 5-day pass-through exception permitting program which contemplates that a “vehicle owner may obtain written approval from the Executive Officer to operate a vehicle for up to five consecutive calendar days without being subject to” 13 CCR 2196.1(a)(1) and (2), which govern the owner operator requirements. 15 The 5-day exemption is available once per calendar year to vehicles with no outstanding enforcement actions. The five days must run consecutively after approval and the application must be sent at least seven business days “prior to the vehicle's planned travel or entry in California.” 16 Vehicle owners must request the exemption in advance through CARB's compliance platform by providing a variety of information, including the vehicle's registration information, vehicle identification number (VIN), relevant dates, and origin and destination information. If granted, the owner must keep the pass document in the vehicle and provide it to CARB inspectors upon request. 14 The HD I/M Regulation permits entities subject to the rule to apply once per calendar year for a 5-day “pass through” exception which must be granted in each instance and on an individualized basis. The EPA notes that California has not provided assurances that this additional compliance step meaningfully changes the coverage of the HD I/M Regulation. 15 13 CCR 2196(d). 16 13 CCR 2196(d)(1). The HD I/M Regulation requires owners of heavy-duty vehicles operating in California (including out-of-state and out-of-country vehicles) to report owner and vehicle information to CARB. It also requires owners of heavy-duty vehicles to demonstrate that their vehicle emissions control systems are properly functioning through vehicle compliance tests completed by CARB-approved testers and to periodically submit vehicle compliance test results to CARB. Vehicles equipped with on-board diagnostic (OBD) systems can be tested using OBD data, while older non-OBD vehicles are subject to smoke opacity and visual inspections. Vehicle owners are also required to have a valid HD I/M compliance certificate with the vehicle while operating in California, which they must present to a CARB inspector and/or California Highway Patrol officer upon request. The HD I/M Regulation also establishes a referee testing network to provide independent evaluations of heavy-duty vehicles and services for vehicles with inspection incompatibilities or compliance issues. Finally, the HD I/M Regulation describes procedures for HD I/M roadside inspections, including roadside monitoring and field inspections. D. What did the EPA propose? On August 26, 2025, the EPA proposed to partially approve and partially disapprove, or, in the alternative, to fully approve, the HD I/M Regulation into the California SIP. 17 While the Agency proposed to find that the submission generally meets applicable requirements of the CAA and implementing regulations, the EPA proposed to partially disapprove because of substantial concerns with allowing provisions in the HD I/M Regulation that purport to regulate vehicles registered out-of-state and out-of-country to become federally enforceable. 17 90 FR 41525, 41527-29. Specifically, the EPA proposed that California had not provided necessary assurances that the State is not prohibited by any provision of Federal or State law from implementing the SIP, as required by CAA section 110(a)(2)(E)(i). The Agency proposed that the Commerce Clause of the U.S. Constitution appears to prohibit implementing the HD I/M Regulation because its extraterritorial reach burdens core instrumentalities of interstate commerce, that is, heavy-duty vehicles used in interstate shipping. The Agency noted that the HD I/M Regulation effectively outsources the costs of emissions reductions within California to other States and regulated entities in those States by requiring compliance with California's inspection and maintenance (“I/M”) regime even when the vehicles are not within California. The Agency also noted that under the structure of CAA section 110, a full approval of the HD I/M Regulation would effectively force regulated entities in other States to comply with California's HD I/M requirements, rather than the applicable requirements in their respective States, including requirements approved by the EPA pursuant to the CAA. Finally, we proposed that the extraterritorial reach of the HD I/M Regulation appears to abrogate the foreign relation powers vested exclusively in the Federal Government by the U.S. Constitution. The EPA further proposed that the extraterritorial reach of the HD I/M Regulation is inconsistent with CAA section 110. The Agency observed that CAA section 110 requires the submission of SIPs by each State and that full approval of the submission would, by making the HD I/M Regulation federally enforceable, potentially result in multiple conflicting sources of obligations. The Agency also noted that the HD I/M Regulation was unusual in this respect and requested comment on all aspects of the proposal, including whether a full approval of the State's submission would raise additional concerns under any other Federal or State law. II. The EPA's Evaluation and Final Action After reviewing California's submission and all comments received during the public comment period, the EPA is finalizing a partial approval and partial disapproval that will allow the HD I/M Regulation to go into effect for CAA purposes except to the extent it applies to vehicles registered outside the State. As previously noted, the CAA expressly requires that a SIP submittal “shall” provide “necessary assurances” that the State “is not prohibited by any provision of Federal or State law from carrying out such implementation plan or portion thereof.” 18 The EPA cannot approve a SIP submission, thereby making it effective for CAA purposes and federally enforceable, unless “it meets all of the applicable requirements of this chapter.” 19 18 CAA section 110(a)(2)(E)(i). 19 CAA section 110(k)(3); see, e.g., Safe Air for Everyone v. EPA, 488 F.3d 1088, 1093 (9th Cir. 2007) (“Before a SIP becomes effective, EPA must determine that it meets the CAA's requirements.”). The EPA determines that California has not provided necessary assurances that the State is not prohibited by Federal law—specifically, the Clean Air Act and the Commerce Clause of the U.S. Constitution—from implementing the HD I/M Regulation to the extent it purports to regulate vehicles registered out-of-state or out-of-country based solely on whether such vehicles traverse California for virtually any length of time. As discussed at proposal and reinforced by several commenters, the State's submission externalizes the cost of additional emissions reductions (out-of-state vehicles that must comply with California's I/M regime on an ongoing basis) to achieve localized benefits (additional emissions reductions that assist California in demonstrating attainment of the NAAQS for the benefit of California residents). The Supreme Court has explained that the “dormant” Commerce Clause prohibits “even nondiscriminatory burdens on commerce” when “those burdens clearly outweigh the benefits of a state or local practice.” Nat'l Pork Producers Council v. Ross, 598 U.S. 356, 392 (2023) (Roberts, C.J., concurring in part and dissenting in part). 20 Such burdens are of particular concern when they impose costs on interstate trade, see, e.g., Kassel v. Consol. Freightways Corp., 450 U.S. 662, 674 (1981) (plurality op.); Raymond Motor Transp., Inc. v. Rice, 434 U.S. 429, 445 & n.21 (1978), where “the nature of” the market means that a State regulation generates costs whether or not participants sell into the regulating State, Nat'l Pork Producers, 598 U.S. at 400 (Roberts, C.J., concurring in part and dissenting in part), and where a State regulation targets “instrumentalities of interstate transportation—trucks, trains, and the like,” id. at 379-80 & n.2 (majority op.); accord id. at 392 (Sotomayor, J., concurring in part). 20 As explained at proposal, a majority of the Court in National Pork Producers affirmatively retained the balancing test in Pike v. Bruce Church, Inc., 397 U.S. 137 (1970), for assessing the validity of State regulations against the “dormant” aspect of the Commerce Clause. 90 FR 41525, 41528 & n.22. In this context, Congress has exercised its exclusive regulatory authority over interstate commerce by enacting CAA section 110 and related provisions specifying States' obligations to attain the NAAQS. Under CAA section 110, “ each State” must develop and submit a plan for implementing, maintaining, and enforcing the NAAQS “ within such State.” 21 As a general matter, the Clean Air Act assigns national regulation, including the regulation of interstate air pollution and standards-setting for mobile sources, to the EPA. For example, title II of the Act authorizes the EPA to set mobile source standards when certain conditions are met and expressly preempts the adoption or attempted enforcement of State standards (including certification, inspection, and approval requirements for sale, titling, or registration) except through the preemption waiver and waiver adoption processes in CAA sections 177 and 209. 22 Similarly, the Act generally does not permit States to outsource the costs of emissions reductions within their borders onto other States except where expressly authorized. 23 Under CAA section 110(a)(2)(D)(i)(I), for example, States must submit plans to restrict certain emissions within their borders if such emissions contribute significantly to nonattainment in other States. 21 CAA section 110(a)(1), (2) (emphases added). 22 See CAA sections 209(a) (preempting the implementation or enforcement of vehicle and engine emission standards, including certification, inspection, and other approval requirements), 209(b) (setting out the process for requesting and issuing a preemption waiver), and 177 (authorizing States to elect to implement standards for which a preemption waiver has been granted under certain conditions). Notably, the title II preemption provision includes a savings clause authorizing State regulation of “the use, operation, or movement of registered or licensed motor vehicles,” suggesting a recognition that State regulatory authority is linked to vehicles registered or licensed by the regulating State. CAA section 209(d) (emphasis added). 23 See generally 13 CCR 2196; see also Comment ID EPA-R09-OAR-2025-0061-0047 (demonstrating how referee locations are “only found in California” and therefore inequitably discriminate against out-of-state residents in both costs imposed and the burdens in seeking to comply). Here, California's SIP submission seeks to remedy local nonattainment by extending the State's regulatory reach to vehicles registered in other States, and even other countries, that happen to traverse the State. As explained at proposal and confirmed in this final action, out-of-state vehicle owners and operators effectively must comply with the HD I/M Regulation given the volume of interstate trucking that passes through California, the uncertainties regarding whether and when a route will cross through California over the course of a year, and the significant penalties associated with failure to comply. This result is not contemplated or authorized by CAA section 110, which requires “each State” to implement the NAAQS “within such State,” and does not fall within any of the exceptional provisions of the Act that contemplate one State reaching into another State in pursuit of air quality improvements within its own borders. This is not a lawful use of the CAA's SIP provisions, which instruct each State to adopt appropriate controls for that State and prohibit the approval of SIPs not supported by “necessary assurances” of legality under Federal and State law. California may adopt and seek approval of a broad range of strategies to promote NAAQS attainment within the State, including by adopting additional controls for vehicles registered within the State. But it cannot (at minimum, without providing necessary assurances) outsource the costs of local attainment to out-of-state and out-of-country vehicle owners and operators through a regulation that would, if approved, become federally enforceable throughout the country in lieu of adopting additional controls for vehicles registered within the State. Nothing in California's submission provides necessary assurances that implementing the HD I/M Regulation in full would not contravene Federal law, and California continues to maintain that its submission not only can, but must, be approved and made federally enforceable under the CAA. While not necessary to the EPA's determination that the SIP submission fails to provide necessary assurances, the HD I/M Regulation also arguably discriminates against out-of-state vehicle owners and operators by externalizing the costs of achieving the local benefits of NAAQS attainment. Nothing about the regulatory goals of the HD I/M Regulation required California to extend compliance requirements to out-of-state vehicles or to make that extension federally enforceable by seeking approval in the State's SIP. Rather than taking this novel approach, California could have limited its application to vehicles registered within the State and adopted additional controls for vehicles registered within the State (or for other sources that emit the relevant pollutants), thereby achieving significant progress toward NAAQS attainment without raising interstate commerce concerns. Indeed, the HD I/M Regulation includes provisions specific to out-of-state vehicles, and CARB separately estimated emissions reductions attributable to in-state and out-of-state vehicles. 24 The choice to extend the regulation to out-of-state and out-of-country vehicles was deliberate and unnecessary to the operation of the regulatory scheme with respect to vehicles registered within the State. In this way, the SIP submittal arguably discriminates against out-of-state vehicles by subjecting them to additional regulatory requirements that apply year-round and regardless of location in exchange for localized benefits. California's legitimate objective, reducing emissions to comply with its NAAQS obligations under Federal law, does not require regulation of all trucks nationwide that may traverse the State, particularly in a manner in which the burdens of compliance fall disproportionately on out-of-state owners and operators as compared to vehicles registered within the State. 25 Put another way, extending the regulation to out-of-state vehicles serves the illegitimate objective of outsourcing the costs of attaining the NAAQS within California to other States and vehicle owners and operators in those States, rather than identifying additional emissions reduction strategies within the traditional ambit of purely in-state sources encompassed within and creditable to the State of California. 24 See Cal. Health & Safety Code §§ 44011.6, 44011.7; see also Staff Report, which breaks out said costs and emissions estimates by in-state and out-of-state operators. 25 See Comment ID EPA-R09-OAR-2025-0061-0044; Comment ID EPA-R09-OAR-2025-0061-0001 (pointing out the national character of the proposed regulation). Additionally, commenters asserted that the regulation imposes itself upon the testing apparatus of other States and unfairly burdens their residents with compliance. See Comment ID EPA-R09-OAR-2025-0061-0025 (pointing out infeasibility of out-of-state testers satisfying CARB). Finally, one commenter points out that in order to challenge supposed violations, out-of-state operators “must request a hearing with the CARB Hearing Coordinator and make arrangements to return to California” thus logistically crippling small business operators with unfair compliance burdens. Comment ID EPA-R09-OAR-2025-0061-0048. The discrimination at issue here is different in kind from the indirect impacts to interstate commerce permitted by the Supreme Court's Commerce Clause jurisprudence. In National Pork Producers, the Court rejected an “almost per se” Commerce Clause challenge to a California law that sought to promote the humane treatment of animals by barring California merchants from selling non-compliant pork within California. 598 U.S. at 367 (majority op.); see also id. at 384 (plurality op.) (emphasizing that the law regulated sales within California and that non-compliant producers remained free to “withdraw from that State's market”). In contrast here, the HD I/M Regulation would, if approved into the SIP, apply directly to and be federally enforceable against out-of-state and out-of-country vehicle owners and operators even if they conduct no business in California. Trucks shipping apples from Washington to Arizona, or export goods from Texas to ports on the Pacific Ocean, would be obligated to comply merely because they passed through California. As already discussed, proactive compliance by many out-of-state interstate shippers would be the only practicable option to avoid noncompliance and significant fines. This extraterritorial scope exceeds the localized scope of California's interest. Nor is California's goal of demonstrating compliance with its statutory obligations, thereby avoiding potential bump-ups in nonattainment level by operation of the statute, directly related to the health, safety, or other interests the Court has recognized as grounds for permissible in-state regulation imposing indirect out-of-state burdens. Id. at 374-75 (majority op.). Rather, the out-of-state reach of the SIP submission is explicitly tied to more effectively meeting California's obligations under the CAA's NAAQS implementation provisions, including deadlines for attainment and reclassification. And the SIP submission's out-of-state reach pursues that goal by imposing costs on interstate trucking, a function the Court specifically noted warrants a more exacting analysis. Id. at 379 n.2 (majority op.) (“[T]his Court [has] refused to enforce certain state regulations on instrumentalities of interstate transportation—trucks, trains, and the like. . . . Nothing like that exists here. We do not face a law that impedes the flow of commerce. Pigs are not trucks or trains.”). 26 26 As noted at proposal and confirmed in this final action, the EPA's full approval of the SIP submittal would also threaten to impose conflicting obligations with respect to I/M requirements. See, e.g., Exxon Corp. v. Gov. of Md., 437 U.S. 117, 128 (1978) (distinguishing between the retail market and regulation that impedes the flow of goods and risks “that the several States will enact differing regulations”). Regardless of whether the regulation at issue here is discriminatory, a showing of discrimination is not required under Pike v. Bruce Church, Inc., 397 U.S. 137 (1970), or related cases. In National Pork Producers, a majority of the Supreme Court “le[ft] the courtroom door open to plaintiffs invoking the rule in Pike, that even nondiscriminatory burdens on commerce may be struck down on a showing that those burdens clearly outweigh the benefits of a state or local practice.” 27 And the Court has long recognized special considerations for instrumentalities of commerce (including interstate trucking). 28 This line of cases is directly on-point and demonstrates that the HD I/M Regulation at issue here warrants careful consideration. The SIP submittal's intended applicability to interstate trucking beyond the borders of California (and that which passes through California, at least on occasion, owing to the nature of the market) appears to contravene case law evaluating State laws which impose undue burdens upon the instrumentalities of interstate commerce. California provided no assurances to the contrary in its SIP submission and continues to maintain its entitlement to impose such burdens under the CAA. As articulated in greater detail in our responses to comments in section III of this preamble, the EPA views the burdens of a fully approved SIP submission on interstate commerce as significant. Such significant burdens outweigh the proposed local compliance benefits of the regulation and therefore run afoul of the Commerce Clause. As one commenter explained: “The program's overreach will result in the potential for de facto regulation of out-of-state rented or leased trucks across the country even though renting and leasing companies have no control [over] whether their trucks' routes include traveling into California. . . . CARB's HD I/M program disproportionately affects out-of-state rental and leasing company operations and finances . . . in clear violation of the Dormant Commerce Clause.” 29 27 598 U.S. at 395-96 (Roberts, C.J., concurring in part and dissenting in part). 28 See id. at 379 n.2 (majority op.) (“[T]here exists a strong line of cases that originated before Pike in which th[e] Court refused to enforce certain state regulations on instrumentalities of interstate transportation—trucks, trains, and the like.”); s ee, e.g., Bibb v. Navajo Freight Lines, Inc., 359 U.S. 520, 523-30 (1959) (concerning a State law specifying certain mud flaps for trucks and trailers); S. Pac. Co. v. Arizona ex rel. Sullivan, 325 U.S. 761, 763-82 (1945) (addressing a State law regarding the length of trains). 29 Comment ID EPA-R09-OAR-2025-0061-0036. Unlike virtually all prior CARB regulations and similar regulations adopted by other States, the HD I/M Regulation would apply to vehicles registered out-of-state and out-of-country that operate within the State of California for almost any length of time. Because approval of a SIP makes its requirements federally enforceable, 30 the regulation would, in effect, become a Federal regulation enforceable by the EPA (and citizen-suit plaintiffs) 31 against any owner or operator in all fifty States of any heavy-duty vehicle that may pass through California. 32 30 CAA section 110(k). 31 CAA sections 113, 304. 32 Comment ID EPA-R09-OAR-2025-0061-0035 (highlighting how the SIP creates duplicative regimes across States increasing compliance costs); Comment ID EPA-R09-OAR-2025-0061-0047 (demonstrating how referee locations are “only found in California” and therefore inequitably discriminate against out-of-state residents in both costs and seeking to comply). As addressed in section III of this preamble, Response to Comments, this would in effect lead to additional compliance costs for heavy-duty vehicle operators in all jurisdictions. Some States have HD I/M provisions that differ from California's in material respects, but none of these have been approved into SIPs. 33 If approved into the SIP in all respects, California's HD I/M Regulation would be federally enforceable to the same extent as other State I/M regulations, including any that may be approved by the EPA in the future pursuant to CAA section 110. The result would be multiple conflicting sources of obligations that are enforceable both within the respective States and federally under the CAA. 33 See 6 NYCRR Subpart 217-5 (New York Heavy Duty Inspection and Maintenance Program), N.J.A.C. 7:27-14 (New Jersey Control and Prohibition of Air Pollution); ORS 815.200-215 (Oregon motor vehicle pollution control); see also Comment ID EPA-OAR-2025-0061-0047 (“Existing HD I/M programs, or new programs adopted in the future, may not all have identical requirements, but any discrepancies are likely to have an immeasurable impact on air quality outcomes provided they are target high-emitting vehicles. Greater assurances are needed that the emissions benefits from these separate programs are properly accounted for and do not overlap.”). Additionally, the SIP would require owners of heavy-duty vehicles to demonstrate that their vehicle emissions control systems are properly functioning through vehicle compliance tests completed by CARB-approved testers and require such owners to periodically submit vehicle compliance test results to CARB to show compliance with the HD I/M Regulation. Vehicles equipped with OBD systems would have to be tested using OBD data, while older non-OBD vehicles would be subject to smoke opacity and visual inspections. Lastly, vehicle owners would be required to have a valid HD I/M compliance certificate with the vehicle while operating in California presentable to a California Highway Patrol officer upon request. As CAA section 202(m) authorizes the EPA to regulate and require such OBD systems for heavy-duty vehicles, the imposition of a State program which would be national in character also risks intrusion into an area reserved to Federal authority. 34 The CAA's requirements and procedures for California to seek and obtain a preemption waiver, and for other States to adopt California standards for which preemption has been waived, do not apply to this submission, and nothing in CAA section 110 suggests that the statute's provisions for SIP development and submission can function as a workaround for the requirements of CAA sections 177 and 209. 34 Comment ID EPA-R09-OAR-2025-0061-0019 (highlighting the creation of conflicting implementation schemes across States imposed by the SIP); Comment ID EPA-OAR-2025-0061-0018 (out-of-state residents being fined for non-compliance with limited options in home State for remediation); Comment ID EPA-R09-OAR-2025-0061-0036 (illustrating how over compliance out of caution is the only prevention from incurring unknown fines from CARB for out-of-state operators); Comment ID EPA-R09-OAR-2025-0061-0048 (pointing out the trespass into Federal authority by CARB's regulation). The impact of California's HD I/M Regulation on vehicles registered out-of-state (and out-of-country) and on interstate shipping is significant. The HD I/M Regulation adds significant costs to operation of heavy-duty vehicles even within California. According to the CARB Staff Report, the HD I/M Regulation will cost $4.12 billion between 2023-2050, with a maximum annual cost of $350 million in 2024. Many of these costs relate to heavy-duty vehicle testing, repair, and compliance fees. 35 But this analysis, which seeks to balance these costs against the benefits of promoting local NAAQS compliance, improperly weighs the benefits to California against costs imposed nationwide. As commenters point out, overcompliance costs and unknowing violations risk fines and burdens imposed outside the borders of California. The EPA notes that many heavy-duty vehicles covered by the regulations at issue are used for purposes of interstate shipping, and that maintenance of those vehicles could occur in any number of States, meaning the burdens of compliance could be felt across the country and even in other countries. The outsourcing of costs and burdens to other States in pursuit of local benefits via the SIP misunderstands the ambit of State regulation and the Commerce Clause limits on the State's powers. The regulatory regime imposed by the SIP, which reports in-state benefits against conservative estimates of out-of-state burdens, calls into question the entirety of the State's cost-benefit analysis as addressed more fully in section III of this preamble. 36 35 Staff Report at IX-14. 36 To cite one example, the Center for Community Action and Environmental Justice refused in its comment to acknowledge the modifications needed to CARB's initial cost-benefit estimates in light of recent resolutions enacted by Congress and signed by the President to void EPA preemption waivers for three California mobile-source regulations. The commenter stated without evidence that this recent legislation is illegal. For that reason, among others, the record includes inconsistent data and estimates with respect to the predicted impacts of the HD I/M Regulation. See Comment ID EPA-R09-OAR-2025-0061-0040. Contrary to claims made by some adverse commenters, the EPA need not specify a less discriminatory approach for California to follow that would comply with the Commerce Clause and therefore render the SIP approvable under the CAA. 37 Under the Pike analysis, the availability of a less discriminatory approach to achieve a regulatory goal is but one of many factors a reviewing court may consider in evaluating whether a State regulation infringes on Federal authority reserved to Congress by the Commerce Clause. 38 When relevant, courts generally place the burden on the regulating State to explain why alternatives that are less burdensome on interstate commerce and out-of-state economic activity were not considered and adopted. 39 The EPA is not required to identify alternatives in this context, including because the CAA's requirement for necessary assurances is a mandatory element of a fully approvable SIP submission. In any event, a less discriminatory alternative is both apparent and reflected in the Agency's proposal: California may achieve significant emissions reductions creditable to NAAQS attainment by implementing the HD I/M Regulation to vehicles registered within the State and, as necessary and appropriate, developing additional controls for in-state registered vehicles and potentially other categories of in-state sources. This final action approves the SIP submittal to that extent while, at the same time, disapproving the submittal to the extent that it purports to infringe on interstate commerce by regulating and burdening interstate trucking. 37 See Comment ID EPA-R09-OAR-2025-0061-0039; Comment ID EPA-R09-OAR-2025-0061-0034; Comment ID EPA-R09-OAR-2025-0061-0019. 38 See, e.g., Hughes v. Oklahoma, 441 U.S. 322, 338 (1979) (invalidating local regulation under the Commerce Clause despite acknowledging “nondiscriminatory alternatives [that] would seem likely to fulfill the State's purported legitimate local purpose”); Granholm v. Heald, 544 U.S. 460, 493 (2004) (discriminatory state regulations may be upheld only after findings that nondiscriminatory alternatives will prove unworkable). 39 See, e.g., Am. Bev. Ass'n v. Snyder, 735 F.3d 362, 376 (6th Cir. 2013) (holding that a Michigan product-labeling requirement violated the Commerce Clause by requiring a unique to Michigan labelling system by out-of-state firms “without the consideration of other less burdensome alternatives”). California's submission does not contain necessary assurances to demonstrate that the HD I/M Regulation can be implemented if approved as to out-of-state and out-of-country vehicles without running afoul of Commerce Clause principles, as required by CAA section 110(a)(2)(E). The SIP rests on a misunderstanding of the reach of the State's regulatory authority and the division of authority between the EPA and the States under the CAA, including CAA section 110. California may regulate I/M activities for vehicles registered within the State consistent with Federal law and may submit such regulation for approval to satisfy the State's NAAQS attainment obligations under Federal law. But the EPA cannot authorize California to become a de facto Federal regulator by making the State's HD I/M Regulation federally enforceable through approval into the SIP. Under the circumstances presented here, approval of the SIP would not be consistent with CAA section 110(a)(2)(E). 40 40 Under the Pike balancing test, that aspect of the regulation appears to place substantial burdens on interstate commerce that are not justified by local benefits. Nor is it clear that the State has a legitimate interest in extending the regulation to out-of-state and out-of-country vehicles for the purpose of satisfying California's obligations to demonstrate compliance with the NAAQS. Under established precedent, benign State objectives in regulation that burdens interstate commerce must balance against the burdens imposed. See Raymond Motor Transp., 434 U.S. at 445 (finding a State law banning vehicle length, despite its potential safety benefits and the presumption of validity afforded to laws passed within a traditional state domain, to be an unconstitutional burden to interstate commerce); Burlington N. R. Co. v. Nebraska, 802 F.2d 994, 1001 (8th Cir. 1986) (“ `Regulations designed for [a] salutary purpose nevertheless may further the purpose so marginally, and interfere with commerce so substantially, as to be invalid under the Commerce Clause.' ” (quoting Kassel, 450 U.S. at 670 (plurality op.)) (holding a State law banning double-trailers unconstitutional based on interstate burden). In response to the proposal, CARB asserted that the HD I/M Regulation, including implementation of its provisions with respect to out-of-state and out-of-country vehicles passing through California, is necessary to demonstrate attainment with the NAAQS in several of the State's air quality regions. According to CARB, the regulation is projected to reduce NO X emissions statewide by approximately 81 tons per day in 2037 and 110 tons per day in 2050, and directly emitted PM 2.5 emissions statewide by approximately 0.7 tons per day in 2037 and 0.9 tons per day in 2050. CARB does not clearly delineate between benefits attributable to in-state vehicles and out-of-state and out-of-country vehicles in this calculation presented in comment. The HD I/M Regulation is additionally expected to reduce NO X emissions in the South Coast Air Basin by approximately 22 tons per day in 2037 and 29 tons per day in 2050, and directly emitted PM 2.5 emissions by approximately 0.2 tons per day in 2037 and 2050. Finally the HD I/M Regulation is expected to reduce NO X emissions in the San Joaquin Valley by over 21 tons per day in 2037 and approximately 30 tons per day in 2050, and directly-emitted PM 2.5 emissions by approximately 0.2 tons per day in 2037 and 2050. But CARB goes on to admit that these regulations extend to out-of-state vehicles by stating that “[o]ver 750,000 vehicles and 260,000 fleets, respectively, are currently registered in the program. The majority of these vehicles and fleets are registered in California.” 41 Thus, CARB acknowledges that the projected emissions reductions attributed to the HD I/M Regulation—which it identifies as needed to discharge statutory obligations to attain the NAAQS—are in no small part reliant on regulating vehicles registered and primarily operating outside of the State. In a comment submission, the Union of Concerned Scientists (UCS) estimates that “[i]n 2025, out-of-state vehicles made up at least 13 percent of [heavy duty vehicles] operating on California's roads and highways [with] . . . out-of-state [vehicles] . . . responsible for more than 34 percent of NO X emissions and over 39 percent of PM 2.5 .” 42 Thus, based on this comment in support of the HD I/M Regulation, over a third of the emission reductions benefits for NAAQS compliance are achieved by impermissibly burdening the citizens and businesses of other States. 41 Comment ID EPA-R09-OAR-2025-0061-0045. 42 Comment ID EPA-R09-OAR-2025-0061-0041; see also Comment ID EPA-R09-OAR-2025-0061-0042 which estimates that “[a]pproximately half of the trucks operating in California are out-of-state or out-of-country” before advocating the “necessit[y] [of] the applicability of the HDIM program [beyond California] to adequately address harmful emissions.” This comment seems to suggest that California has the authority to seek to regulate all jurisdictions globally under this program and should seek to exercise such authority. Relatedly, the EPA determines that California's submission cannot be approved in full because it conflicts with CAA section 110 and related provisions of the statute. The EPA's concern in this respect is heightened by the structure of CAA section 110 and the way in which a full approval of the HD I/M Regulation would operate on the ground. In effect, an approval would delegate to California the ability to enforce the State's I/M requirements throughout the nation to the extent a vehicle passes through or operates within the State for virtually any length of time. As commenters make clear, the nature of the trucking industry ensures that almost all out-of-state operators would be forced into compliance to avoid unknowing and incidental violations of these requirements. As a result, an approval would effectively force regulated entities in other States to comply with California's HD I/M requirements, rather than the applicable requirements in their respective States, including requirements approved by the EPA pursuant to the CAA. 43 That interstate regulatory function is vested exclusively in Congress by the Commerce Clause, and the result of the EPA's approval under the circumstances risks precisely the abrogation of Federal authority that the Supreme Court has held the Commerce Clause prohibits. 43 As noted elsewhere in this preamble and by commenters, burdens on out-of-state and out-of-country owners and operators would be more significant than for in-state vehicles to the extent CARB-approved testers and other necessary compliance steps are not readily available outside California. The Commerce Clause analysis discussed in this section follows from the Supreme Court's recognition that the Clause contains “a negative command” that forbids “certain state [economic regulations] even when Congress has failed to legislate on the subject.” Okla. Tax Comm'n v. Jefferson Lines, Inc., 514 U.S. 175, 179 (1995). Here, Congress has affirmatively legislated on the subject by providing the framework for States to implement CAA requirements for attaining the NAAQS, subject to EPA approval. CAA section 110 requires “[e]ach State” to “adopt and submit to the Administrator . . . a plan which provides for implementation, maintenance, and enforcement” of the NAAQS “within such State.” 44 In addition to the role carved out for “[e]ach State,” Congress vested the EPA with exclusive authority to promulgate standards and regulations relevant to attainment, including the NAAQS themselves under CAA sections 108 and 109 and generally applicable regulations that lower emissions under CAA sections 111 and 202, among other provisions. As discussed at proposal, approving California's HD I/M Regulation in full—and thereby making it federally enforceable—interferes with this statutory scheme by placing California in the driver's seat across all fifty States. 44 CAA section 110(a)(1). If approved, California's regulation would be federally enforceable against any heavy-duty vehicle that may pass through California, although those vehicles may already be subject to I/M regulations applicable in the State of registration. Thus, a vehicle registered in any other State would be subject to both its own local state laws and the California SIP overlaid and enforceable under Federal law. California law would effectively take precedence over any other State's, and over applicable EPA regulations. In addition, approval of California's regulation would create an inherent tension with any other State seeking to adopt an HD I/M regulation into a SIP as part of an emissions reduction strategy. Courts have held that all measures used to attain the NAAQS must be included in the relevant State's SIP. 45 If another State seeks SIP approval for an HD I/M regulation that is less stringent than or different from California's, and if the EPA approves such a SIP submission, vehicles may be subject to multiple federally enforceable I/M requirements that differ from or contradict each other. And if the EPA denies such a SIP submission by another State in order to avoid this result, the approval of California's SIP submission will have effectively barred other States from utilizing the same strategy as California to comply with Federal NAAQS obligations under CAA section 110. California alone would be able to benefit its own residents in complying with NAAQS requirements at the expense of other States' residents. Nor do the CAA's SIP provisions contemplate California using its SIP submission to pressure other States seeking to obtain emissions reductions from an I/M program to adopt regulations identical to California's. Even if another State submitted an identical regulation, it would be unclear whether and how much emissions reductions could be attributed to that State's SIP rather than California's program. The CAA provides specific requirements and procedures where California seeks to obtain a preemption waiver and other States seek to follow California's regulations—CAA sections 177 and 209—that are not applicable to this SIP submission under CAA section 110. 45 See Comm. for a Better Arvin v. EPA, 786 F.3d 1169, 1176-77 (9th Cir. 2015). Therefore, pursuant to CAA section 110(k)(3), the EPA is partially approving the HD I/M Regulation into the California SIP to the extent the regulation applies to vehicles registered in the State. This partial approval action incorporates into the California SIP the submitted regulations in table 1 of this preamble and will replace the Heavy-Duty Vehicle Inspection Program 46 (HDVIP) and Periodic Smoke Inspection Program 47 (PSIP) that were previously approved by the EPA into the California SIP. 48 Our partial approval will also incorporate into the SIP the OBD Standards document that is incorporated by reference through the HD I/M Regulation. 46 CCR Title 13, Division 3, Chapter 3.5. 47 CCR Title 13, Division 3, Chapter 3.6. 48 87 FR 27949 (May 10, 2022). Our partial disapproval of the HD I/M Regulation will not result in imposition of either sanctions or a Federal Implementation Plan (FIP). Sanctions are not imposed under CAA section 179(b) because the submittal of the HD I/M Regulation is discretionary ( i.e., not required to be included in the SIP), and the EPA need not promulgate a FIP under CAA section 110(c)(1) because the partial disapproval does not reveal a deficiency in the SIP that such a FIP must correct. The submitted regulation has been adopted by the State of California, and our partial disapproval will not by its own force prevent the State from enforcing it within California as a matter of State law. 49 49 The EPA's role in this action is limited to determining whether and to what extent the SIP submission is approvable. That analysis turns on determining whether the SIP submission satisfies all applicable requirements of the CAA, including the requirement that California provide “necessary assurances” that the SIP could be implemented consistent with Federal and State law. Thus, this final action is not a determination of the constitutionality of the HD I/M Regulation and should not be read as purporting to decide whether California may, consistent with the Commerce Clause, continue to enforce the regulation as a matter of State law. III. Response to Public Comments and Discussion The EPA's proposed rulemaking provided a 30-day public comment period, in which we sought comments on all aspects of the proposal, including both proposed alternatives and related issues. During this period, we received a total of 42 comments. This section summarizes and responds to all comments that are germane to this action. 50 50 The comments included one non-germane comment, which we have not addressed, and one comment that included profanity, which we have not addressed and which is not included in the docket for this action. See “Commenting on EPA Dockets,” https://www.epa.gov/dockets/commenting-epa-dockets. A. Comments in Support of Partial Disapproval Comment 1: General Support for Partial Disapproval Several commenters expressed general support for the EPA's proposed partial disapproval of the HD I/M Regulation as applied to vehicles registered outside the State of California for the reasons addressed in the proposed rulemaking. These reasons relate to the EPA's substantial concerns that California had not provided necessary assurances of adequate authority under CAA section 110(a)(2)(E)(i) to implement the HD I/M Regulation as it applies to vehicles registered in other States and other countries consistent with Federal law, including the Commerce Clause and foreign relations powers provisions of the U.S. Constitution, as well as substantial concerns that EPA approval of the HD I/M Regulation could result in conflicts with provisions of other States' SIPs. Response: The EPA appreciates these comments. For reasons addressed in this preamble and consistent with the primary proposal, we are finalizing a partial approval and partial disapproval of the HD I/M Regulation. Comment 2: Burdens to Interstate Commerce Several commenters described specific burdens to interstate commerce that they believed supported partial disapproval of the HD I/M Regulation, including costs to out-of-state vehicles and the industry generally, and difficulties associated with compliance. The National Tank Truck Carriers (NTTC) expressed concerns related to operational feasibility, noting logistical and legal uncertainty associated with applying the HD I/M Regulation to vehicles registered outside of California. The commenter described negative impacts of California's Advanced Clean Trucks (ACT) and Low NO X Omnibus regulations, and stated that applying similar rules to out-of-state vehicles would undermine emission reduction goals and increase costs and operational inefficiencies. The Bennett Family of Companies described costs associated with testing equipment, testing certification, downtime, administrative burdens, and equipment requirements, which they argue harms efficiency and competitiveness in interstate trade. The commenter also cited delays resulting from roadside enforcement compliance checks and restrictions on non-compliant vehicles, and associated supply chain disruptions particularly for time sensitive freight and deliveries, and noted inefficiencies associated with conflicting State requirements. The American Trucking Associations (ATA) also described impacts of delays and difficulties associated with testing requirements especially for out-of-state fleets that are located far away from testing facilities and referee services and noted that fleets are sometimes classified as non-compliant despite their best efforts to comply. The commenter stated that the cost and time needed to test vehicles that operate in California for only a few hours or days likely outweigh the emissions benefits to California. The Owner-Operator Independent Drivers Association (OOIDA) described costs associated with compliance as well as fines for noncompliance, and noted practical difficulties for operators based outside of California to challenge citations issued under the regulations. The commenter included examples of citations issued to businesses located outside of California. Several commenters noted that costs and penalties associated with the HD I/M Regulation may disproportionately impact small carriers and owner-operators who lack resources to absorb the added expenses. 51 Small proprietors also commented on the disproportionate burdens to interstate commerce they would suffer in being forced of necessity to treat the HD I/M Regulation as a national standard mandating fleet replacement, out-of-state permitting hurdles, fines levied against non-California-based businesses, and downstream burdens to other industries in need of transportation services. 52 One example provided in a comment from the Truck Renting and Leasing Association (TRALA), explains how a business with an out-of-state rented or leased truck may not even be aware of its fleets operation in California until “the owner's receipt of a CARB citation . . . [s]uch citations can lead to enforcement actions with potential fines reaching up to $10,000 per day.” 53 Finally, a comment from the California Trucking Association explains the unaccounted for administrative burdens caused by enforcement of the HD I/M Regulation and the practical impossibility of certain carriers to usefully comply with the regulation as promulgated. 54 51 See generally Comment ID EPA-R09-OAR-2025-0061-0048. 52 See generally Comment ID EPA-R09-OAR-2025-0061-0015; Comment ID EPA-R09-OAR-2025-0061-0016; Comment ID EPA-R09-OAR-2025-0061-0018. 53 Comment ID EPA-R09-OAR-2025-0061-0001. 54 See generally Comment ID EPA-R09-OAR-2025-0061-0037. Response: The EPA recognizes the substantial compliance costs associated with the HD I/M Regulation, including those to vehicles registered outside the State, and the accompanying burdens to interstate commerce, including those that are unique to or more significant for out-of-state and out-of-country registered vehicles. The impact of California's HD I/M Regulation on vehicles registered out-of-state and on interstate shipping is undoubtably significant. The HD I/M Regulation adds significant costs to operation of heavy-duty vehicles registered in California. According to a CARB 55 Staff Report, the HD I/M Regulation will cost $4.12 billion between 2023-2050, with a maximum annual cost of $350 million in 2024. Much of these costs relate to heavy-duty vehicle testing, repair, and compliance fee costs. 56 CARB estimated the total direct costs on single-vehicle fleets and “typical” ( i.e., seven-vehicle) fleets. But as articulated by the above comments, CARB's analysis does not properly account for the myriad costs imposed on out-of-state operators forced to comply with the regulatory program. The cumbersome reporting obligations, fleet updating, and narrow windows for reporting impose additional costs to out-of-state vehicle operators. 57 To the extent the HD I/M Regulation applies to out-of-state and out-of-country vehicles that pass through California for almost any length of time, this cost structure would also be imposed on other States and regulated entities in those States. The EPA notes that many heavy-duty vehicles covered by the regulations at issue are used for purposes of interstate shipping, and that maintenance of those vehicles could occur in any number of States, meaning the burdens of compliance could be felt across the country and even in other countries. The overcompliance which the commenters assert such a regime will create represents unwarranted and substantial burdens on out-of-state fleets. 58 55 Staff Report at IX-14. 56 Staff Report at IX-18 through 20. CARB states that, according to vehicle registration data, of fleets consisting of at least three vehicles, 75 percent have four to ten vehicles. 57 See generally Comment ID EPA-R09-OAR-2025-0061-0037; Comment ID EPA-R09-OAR-2025-0061-0048. 58 Comment ID EPA-R09-OAR-2025-0061-0037. As described in this preamble, our partial disapproval of the HD I/M Regulation considers these costs among other considerations and finds that the substantial burdens placed upon out-of-state instrumentalities of interstate commerce appear to run afoul of the Commerce Clause as explained below in further response to comments. CAA section 110(a)(2)(E) provides that a SIP must include “necessary assurances” that the State “is not prohibited” by any Federal law, and California has not provided such assurances. In accessing compliance with the Federal Constitution, the cost burdens of the SIP support the need for partial disapproval. While not directly relevant to this rulemaking, we would like to clarify in response to NTTC's comment regarding California's ACT and Low-NO X Omnibus regulations that the HD I/M Regulation does not and legally cannot expand the scope of these regulations to any additional vehicles or areas. These measures were permitted to go into effect by EPA waivers of preemption that were disapproved by Congress and the President under the Congressional Review Act in 2025 and are therefore preempted and without legal force. 59 59 See H.J. Res 87 (April 30, 2025) (disapproving April 6, 2023 waiver for ACT); H.J. Res 89 (April 30, 2025) (disapproving January 6, 2025 waiver for Low-NO X Omnibus). On June 12, 2025, President Trump signed these Congressional Review Act resolutions disapproving the waivers. See also Statement by the President June 12, 2025, https://www.whitehouse.gov/briefings-statements/2025/06/statement-by-the-president/. Comment 3: Discrimination Under Commerce Clause; Less Burdensome Approaches Several commenters specifically argued that the HD I/M Regulation violates the Commerce Clause under applicable judicial interpretations, including the presence of less burdensome regulatory approaches. TRALA argued that the HD I/M Regulation is discriminatory under the Dormant Commerce Clause because it compels out-of-state rental and leasing businesses to “over-comply” for vehicles that do not enter California in order to ensure that their fleet is in full compliance, because the regulations do not differentiate between the amount of emissions generated by specific trucks (including out-of-state trucks traveling minimally in California), and because requirements to induce vehicle maintenance included in Federal heavy-duty emissions standards enacted in 2022 represent a less discriminatory alternative. The California Trucking Association (CTA) and ATA suggested alternative regulatory approaches raised during CARB's development of the HD I/M Regulation that they argue would be less burdensome. These include exemptions for new vehicles, and measures to focus testing and enforcement resources on fleets and vehicles identified as high emitters, and changes to the reporting schedule to better accommodate the time between purchase and physical delivery of new vehicles. Response: As a general matter, alternative regulatory approaches are outside the scope of this action for reasons described throughout this preamble, including in response to Comment 17. However, the EPA recognizes that courts have considered the availability of less discriminatory approaches as part of Dormant Commerce Clause analysis in some situations. Under the Pike balancing test, whether a less discriminatory approach to a regulatory goal was available is but one of many factors a reviewing court may consider in evaluating whether a regulation violates the Commerce Clause. Regardless of that analysis and whether the HD I/M Regulation at issue here could be found to be discriminatory, the assurances provided for the HD I/M Regulation do not satisfy CAA section 110(a)(2)(E)'s requirement that the proposed SIP include necessary assurances that its implementation would not violate Federal law. Regardless of alternative approaches, the portion disapproved by the EPA in this final action appears to fail the current test for a nondiscriminatory law by placing an improper burden on interstate commerce as prohibited by the Commerce Clause and applicable provisions of the CAA representing Congress' affirmative legislation on the subject. California has not provided necessary assurances to the contrary. As explained previously, there are obvious alternatives for California to achieve its goal of discharging NAAQS-related obligations under Federal law that do not raise similar constitutional and statutory concerns. In response to comments from TRALA, we note that the HD I/M Regulation includes a 5-day “pass-through” exception once per calendar year for individual vehicles that travel only minimally within the State. For a fuller articulation of why this yearly “pass-through” provision does not alter the HD I/M Regulation's national reach or burdens to interstate commerce, please see the discussion in response to Comment 8 and discussion elsewhere in this preamble. Comment 4: Specific Conflicts With Other State Rules ATA stated that other counties and States maintain annual or semi-annual inspection and maintenance programs as part of their truck registration process requirements, citing programs in Colorado, New York, and New Jersey. The commenter noted that the HD I/M Regulation presumes noncompliance even for trucks that were recently inspected in another area. The commenter described these programs as redundant and costly, and argued that they raise concerns regarding claimed program benefits. Response: We appreciate this comment. As described in the preamble to the proposed rule and in this preamble, we considered the possibility of conflicts with other States' laws as a basis for our final action. The EPA is partially disapproving the SIP submission because California has not provided necessary assurances that the extraterritorial reach of the HD I/M Regulation into other States and burdens imposed on interstate commerce do not violate CAA section 110 and related provisions by infringing upon, or frustrating the implementation of, SIPs submitted by other States and reviewed by the EPA. If approved in all respects, California's HD I/M Regulation would be federally enforceable to the same extent as other State I/M regulations potentially approved by the EPA in the future pursuant to CAA section 110. The result is potentially multiple conflicting sources of obligations that are enforceable both within the respective States and federally under the CAA. B. Comments in Support of Full Approval Comment 5: General Support for Full Approval Several commenters expressed support for the EPA's alternative proposal to fully approve the HD I/M Regulation, including its application to out-of-state and out-of-country vehicles, for the reasons addressed in the preamble to the proposed rulemaking. These comments generally argued that the submittal complies with the CAA and applicable regulations, including in particular that California has provided necessary assurances that it has adequate authority to implement the HD I/M Regulation and that implementation of the HD I/M Regulation would not be prohibited by Federal or State law, as required by CAA section 110(a)(2)(E)(i). Response: The EPA acknowledges these comments. However, for reasons addressed in the preamble to the proposed rulemaking and this preamble pertaining to the requirement that SIPs must meet all applicable CAA requirements—specially including “necessary assurances” that the State is not prohibited by any Federal law from carrying out the implementation of the SIP—we are finalizing a partial approval and partial disapproval of the HD I/M Regulation. The State did not provide necessary assurances that implementation of the HD I/M Regulation as applied to all non-gasoline combustion vehicles above 14,000 lbs that pass through California, including vehicles registered out-of-state and out-of-country, would not be prohibited by Federal law. Comment 6: Other Practical Considerations Supporting Full Approval Several commenters described health and environmental benefits associated with the HD I/M Regulation, as well as other practical considerations in favor of the HD I/M Regulation and/or its approval into the SIP, including those related to the role of the emissions reductions associated with the HD I/M Regulation in regional attainment planning in California. Commenters described health impacts associated with ozone and PM 2.5 emissions, including disease and premature death, and cited a need for reductions of ozone, PM 2.5 , and their precursors particularly within the South Coast and San Joaquin Valley nonattainment areas. Commenters described the role of emissions from heavy-duty vehicles generally and from out-of-state heavy-duty vehicles in particular, citing figures from CARB's SIP submittal and other sources. Commenters pointed to predicted reductions in PM 2.5 and NO X associated with the HD I/M Regulation, which commenters asserted are relied upon in several PM 2.5 and ozone plans, and argued that it would be difficult and costly to obtain equivalent reductions from other mobile or stationary sources. Commenters also cited confusion, regulatory uncertainty, and other practical concerns that could result from partial disapproval of the HD I/M Regulation. The Center for Community Action and Environmental Justice and Sierra Club (collectively, “CCAEJ”) argued that a partial disapproval of the HD I/M Regulation would reduce the amount of SIP creditable emissions reductions from the HD I/M Regulation, and that the EPA would be obligated to promulgate a FIP if California fails to submit an attainment demonstration or if the EPA disapproves an attainment demonstration that the State fails to correct. One anonymous commenter argued that heavy-duty trucks emit the same pollutants regardless of where they are registered, and that not regulating out-of-state vehicles would create a “regulatory loophole” that would unfairly burden in-state vehicles and undermine the State's ability to address air pollution. The UCS argued that partial disapproval would be inconsistent with the EPA's commitment to ensuring that Americans have access to clean air, as described in the first “pillar” of the “Powering the Great American Comeback” Initiative announced in a recent EPA press release. CARB argued that the HD I/M Regulation has been successfully implemented and has achieved emissions reductions as designed, citing statistics regarding vehicle registration, testing and monitoring results, and costs, and that the HD I/M Regulation is consistent with other CARB in-use regulations that the EPA has previously approved into the SIP. The commenter argued that partial disapproval of the HD I/M Regulation would transfer the obligation to obtain emissions reductions in part to sources regulated primarily by the Federal Government. Response: We appreciate the considerations raised by the commenters. However, the question before the EPA in this final action is whether the SIP submission may be fully approved, and therefore made federally enforceable, because it does or does not satisfy all applicable requirements of the CAA. The CAA does not authorize the EPA to approve or adopt any provision simply because it may result in projected emissions reductions. For the reasons addressed in the preamble to the proposed rulemaking and in this preamble, we are finalizing a partial approval and partial disapproval of the HD I/M Regulation based on our findings that application of the HD I/M Regulation to vehicles registered outside California does not meet the applicable criteria for SIP approval. The EPA does not agree with commenters' assertions that the SIP submission being partially disapproved is consistent with other CARB regulations that have been approved into California's SIP. As noted elsewhere in this preamble, the EPA sought comment at proposal whether California or any other State had received approval for the portion of the SIP submission at issue here, i.e., the application of an I/M program in one State to vehicles registered and primarily operating out-of-state and out-of-country. Commenters did not provide, and the EPA is not aware of, any examples of a State attempting to assert such regulatory authority nationwide or of the Agency making such a submission federally enforceable by approval into a SIP. The submission before us is novel in this respect, and commenters arguing that the regulation operates similarly to prior I/M programs fail to grapple with this unprecedented distinction or the way this novel submission has forced the EPA to grapple with the issues addressed at proposal and in this preamble for the first time. Furthermore, as explained in this preamble, partial disapproval of the HD I/M Regulation will not result in the imposition of sanctions or require the promulgation of a FIP. Sanctions are not imposed under CAA section 179(b) because the submittal of the HD I/M Regulation is discretionary ( i.e., not required to be included in the SIP), and the EPA need not promulgate a FIP under CAA section 110(c)(1) because the partial disapproval does not reveal a deficiency in the SIP that such a FIP must correct. CAA section 110 places the responsibility to implement the NAAQS on “each State” in the first instance, and partial disapproval of the HD I/M Regulation does not trigger a FIP obligation under the statute because this particular submittal is not mandated by the statute. The submitted regulation has been adopted by the State of California, and our partial disapproval will not by its own force prevent the State from enforcing it within California as a matter of State law, as discussed previously. Commenters incorrectly assumed that California's only path to attainment is through the disproved portion of the SIP submission. Rather, as discussed elsewhere in this preamble, California retains discretion to design programs that promote NAAQS attainment, so long as those programs are consistent with applicable law. This partial disapproval does not prevent California from pursuing additional reductions through controls on in-state mobile or stationary sources that do not raise the same constitutional and statutory concerns. 60 If and when California develops such strategies, it must submit them to the EPA for approval to be credited for emissions reductions in connection with NAAQS attainment. 60 CCAEJ cites the Ninth Circuit's decision in Committee for a Better Arvin for the proposition that “all measures on which a SIP relies to comply with the Act must be approved by EPA as part of the SIP.” Comment ID EPA-R09-OAR-2025-0061-0040. But in that case, the EPA approved a SIP with control strategies based “in significant part on reductions that [would have] been achieved through waiver measures” that were not included in the SIP itself and therefore were not enforceable under the CAA's citizen suit provisions. 786 F.3d at 1176. Nothing in Committee for a Better Arvin stands for the proposition that the EPA must approve an unapprovable SIP submission. Rather, that case supports the EPA's position here by establishing that California and other States cannot be credited for emissions reductions in support of NAAQS attainment unless the relevant control strategies have been included in an approved SIP, which means that the control strategies are consistent with applicable CAA requirements. Because we are partially approving the SIP submission to the extent the HD I/M Regulation applies to vehicles registered within the State, this final action allows California to receive credit for those emissions reductions and does not disrupt ongoing implementation efforts within the State as to such vehicles. Additional considerations relating to the benefits of the HD I/M Regulation as relevant to Commerce Clause considerations are provided in our response to Comment 7. Comment 7: Dormant Commerce Clause—Pike Balancing Several commenters questioned the EPA's proposed basis for partial disapproval related to concerns that the extraterritorial reach of the HD I/M Regulation is prohibited by the Commerce Clause of the U.S. Constitution. Commenters cited caselaw establishing the Supreme Court's approach to evaluating Commerce Clause issues, including the balancing test outlined in Pike. Commenters also pointed to cases considering what kinds of State regulatory burdens to out-of-state interests could run afoul of a Commerce Clause analysis. 61 Commenters argued generally that the HD I/M Regulation does not discriminate against interstate commerce either facially or in purpose or effect, asserting that the HD I/M Regulation generally applies the same requirements to in-state and out-of-state vehicles and does not otherwise economically advantage in-state vehicles or interests. Several commenters described the HD I/M Regulation as providing a “level playing field” for in-state and out-of-state vehicles, while others argued that the HD I/M Regulation is more stringent for in-state fleets and vehicles because of the “5-day pass” option available to out-of-state vehicles and because of supposedly lower compliance costs for out-of-state fleets. 61 See, e.g., Bibb, 359 U.S. at 523-30 (concerning a State law specifying certain mud flaps for trucks and trailers); S. Pac. Co., 325 U.S. at 763-82 (addressing a State law regarding the length of trains). Several commenters criticized the EPA's analysis for failing to consider in-state benefits of the HD I/M Regulation as documented in the materials included with the State's SIP submittal, arguing that this information is relevant to the Pike balancing test or otherwise needed for a Commerce Clause analysis. Commenters argued that the compliance burdens associated with the HD I/M Regulation are not “clearly excessive” relative to local benefits, and that the HD I/M Regulation therefore does not violate the Commerce Clause as applied to out-of-state trucks. The South Coast Air Quality Management District (SCAQMD) stated that conservative estimates show the health benefits of the HD I/M Regulation to be approximately 11 times the compliance costs. Other commenters described benefits of HD I/M Regulation exceeding costs by approximately 18 times based on CARB estimates included in the SIP submittal, while noting that CARB expects HD I/M Regulation to result in additional benefits not included in that calculation. CCAEJ estimated the benefits of the HD I/M Regulation as applied to vehicles registered outside of California to exceed costs for those vehicles by more than 10 times, citing CARB estimates of the impact of vehicles registered outside of California. The Center for Applied Environmental Law and Policy, Environmental Defense Fund, and Natural Resources Defense Council (collectively, “CAELP”) cited previous unsuccessful Commerce Clause challenges to California pollution-control measures and argued that similar claims brought against the HD I/M Regulation would fail for the same reasons. The commenter also noted that CARB received comments during its development of the HD I/M Regulation that alleged Commerce Clause violations associated with the $30 compliance fee, and that CARB's response to these comments was consistent with Supreme Court case law that the commenter described as allowing State regulators to charge a flat regulatory fee on interstate commercial trucks. CARB offered arguments that the HD I/M Regulation complies with the Commerce Clause and is well within the State's authority. The commenter highlighted the Supreme Court's recent decision in National Pork Producers and other cases. 62 The commenter argued that the HD I/M Regulation does not regulate extraterritorially, that the identified burdens are not “substantial” or “significant” enough to trigger application of the Pike balancing test, and that the HD I/M Regulation does not involve discrimination or serious disruptions in the flow of interstate goods. Even if Pike balancing were appropriate, the commenter said, the benefits associated with the HD I/M Regulation overwhelm the burdens, and the EPA's supposed failure to consider those benefits would be arbitrary and capricious. Finally, the commenter argued that benefits associated with the HD I/M Regulation would carry added weight in a balancing test because they relate to Federal legislative and executive branch CAA policy. 62 See Comment ID EPA-R09-OAR-2025-0061-0045 (“To the extent that other burdens—having nothing to do with discrimination—are cognizable under Pike, it is “only when a lack of national uniformity would impede the flow of interstate goods.” (citing 397 U.S. at 380 n.2)). As explained below, however, this lack of national uniformity and proliferation of burdens on interstate trucking is precisely the concern raised by the application of the HD I/M Regulation to out-of-state and out-of-country registered vehicles, particularly if made federally enforceable by approval into California's SIP. Unlike, for example, the Supreme Court's decision in Exxon Corp. v. Governor of Maryland, 437 U.S. 117, 127-28 (1978), the HD I/M Regulation would not apply only to activities within the State and would impact interstate shipping beyond California's borders. Commenters' citation to California Trucking Ass'n v. Bonta, No. 24-2341, 2025 WL 1419921 (9th Cir. May 16, 2025) (unpub.), is equally unpersuasive, since that case involved a State law governing truck driver classifications as independent contractors. This case had nothing to do with trucks as instrumentalities of interstate commerce and does not implicate Pike or its antecedents. Response: At proposal, the EPA noted that the Supreme Court's Commerce Clause jurisprudence forbids State laws that place burdens on interstate commerce that are “clearly excessive in relation to the putative local benefits.” 63 Additionally, in National Pork Producers, “six Justices of [the] Court affirmatively retain[ed] the longstanding Pike balancing test for analyzing Dormant Commerce Clause challenges to state economic regulations.” 64 A plurality of the Court affirms that “[they] generally leave the courtroom door open to plaintiffs invoking the rule in Pike, that even nondiscriminatory burdens on commerce may be struck down on a showing that those burdens clearly outweigh the benefits of a state or local practice.” 65 This is especially relevant here as the Supreme Court recognized special considerations for instrumentalities of commerce (including interstate trucking). 66 This line of cases is directly on-point and suggests that the HD I/M Regulation at issue here must receive particularly close review. The submittal's intended applicability to interstate trucking— i.e., operators, businesses, and trucks registered out-of-state and out-of-country that merely pass through California—facially and directly burdens interstate commerce with significant costs and uncertainties. As noted previously, this concern is not limited to the Pike analysis or even to Commerce Clause constraints on State authority. Here, Congress has legislated on the subject to providing that “each State” must develop its own plans for implementing the NAAQS “within” its borders and that the EPA, rather than California or any State, is authorized to establish national standards that “level the playing field” and further nationwide environmental goals. 63 Pike, 397 U.S. at 142. 64 598 U.S. at 403 (Kavanaugh, J., concurring in part and dissenting in part); see id. at 391 (Sotomayor, J., joined by Kagan, J., concurring in part); id. at 394 (Roberts, C.J., joined by Alito, Kavanaugh, and Jackson, JJ., concurring in part and dissenting in part). 65 Id. at 396 (Roberts, C.J., concurring in part). 66 See id. at 379 n.2 (“[T]here exists a strong line of cases that originated before Pike in which th[e] Court refused to enforce certain state regulations on instrumentalities of interstate transportation—trucks, trains, and the like.”); see, e.g., Bibb, 359 U.S. at 523-30 (concerning a State law specifying certain mud flaps for trucks and trailers); S. Pac. Co., 325 U.S. at 763-82 (addressing a State law regarding the length of trains). None of the cases relied upon by adverse commenters support the overbroad contention that the HD I/M Regulation is immune to the “necessary assurances” analysis involving the Commerce Clause and the reach of State regulation because, in commenters' view, it is non-discriminatory, does not regulate outside California's borders, and does not unduly burden interstate commerce. For example, CAELP cites several cases that did not decide whether the regulations at issue were infirm under the Pike balancing test 67 and did not involve a regulatory context where, as here, out-of-state and out-of-country registered vehicles must comply with the State's regulatory requirements in other States. 68 Moreover, these commenters mistake the relevant analysis here—whether California provided “necessary assurances” that its SIP could, if fully approved, be implemented consistent with Federal law—for the distinct question whether courts would invalidate the HD I/M Regulation if presented with constitutional claims. We do not purport to be adjudicating the ultimate constitutionality of the HD I/M Regulation and, by the same token, need not determine that a reviewing court would be certain to invalidate the regulation if presented with such claims in order to conclude that California failed to provide “necessary assurances” that implementation could proceed lawfully if the regulation were approved in full and made federally enforceable. At least one of the cases cited by commenters recognized that the State's regulation “pushes a state's legal authority to its very limits,” 69 and the CAA does not require the EPA to identify those limits with precision before concluding that a SIP submission is not supported by “necessary assurances” of legality. 70 Moreover, commenters' arguments do not address the propriety of California's HD I/M Regulation under the CAA, which as a matter of text and structure does not support the conclusion that one State may obtain additional creditable emissions reductions by obtaining approval of a SIP that renders its program mandatory and enforceable in other States against owners and operators registered in those States who may traverse California at some point in time. 67 Comment ID EPA-R09-OAR-2025-0061-0043; see Rocky Mt. Farmers Union v. Corey, 730 F.3d 1070 (9th Cir. 2013) (reversing district court finding of discrimination but remanding for analysis under Pike ); Pac. Merch. Shipping Ass'n v. Goldstene, 639 F.3d 1154 (9th Cir. 2011) (affirming denial of summary judgment of certain constitutional claims regarding marine vessel regulations without addressing Pike ); Cent. Valley Chrysler-Keep v. Witherspoon, 456 F. Supp. 2d 1160, 1183-86 (C.D. Cal. 2006) (granting judgment on the pleadings against challenge to certain CARB emission standards on the ground that Congress authorized California to adopt and enforce such regulations if granted a waiver by the EPA under CAA section 209(b)). 68 See Rocky Mt. Farmers, 730 F.3d at 1080 (addressing fuel standards that applied to fuels used “within the California market”); Pac. Merch. Shipping Ass'n, 639 F.3d at 1158-60 (addressing marine vessel regulation that required use of cleaner fuels within California territorial waters). 69 Pac. Merch. Shipping Ass'n, 639 F.3d at 1162. 70 While not necessary to the basis for this partial disapproval, the EPA notes that courts often construe statutes, including those administered by the Agency, to avoid constitutional concerns without determining whether the contrary interpretation would certainly result in a constitutional violation. See, e.g., Inhance Techs., L.L.C. v. EPA, 96 F.4th 888, 893-95 (5th Cir. 2024) (citing, among other cases, Jennings v. Rodriguez, 583 U.S. 281, 286 (2018)). Courts have applied this rationale to Commerce Clause challenges by interpreting State enactments to apply only within the relevant State. See, e.g., Yamaha Motor Corp. v. Team Bozeman Motorsports & Mont. Power Sports Dealers Ass'n, 2009 U.S. Dist. LEXIS 147970, at *6 (D. Mont. Aug. 24, 2009) (interpreting Montana regulation governing motorsports vehicle dealers to apply only to dealers operating within the State). Commenters cited to the EPA's approval of California's Warehouse Indirect Source Rule as indicating that we understand the significant role played by heavy-duty vehicles in emissions and NAAQS attainment. 71 But that observation does not support commenters' conclusion that this SIP submission must be approved because it contained “necessary assurances” that its implementation would not violate Federal law. Unlike the regulation at issue in the cited prior approval action, the HD I/M Regulation purports to regulate heavy-duty vehicle owners and operators directly by requiring I/M activities that must necessarily occur outside the State of California notwithstanding the laws of the State in which they are registered or primarily operate. 71 Comment ID EPA-R09-OAR-2025-0061-0040 (citing 89 FR 73568 (September 11, 2024)). As articulated in the response to Comment 8 below, the EPA views the burdens of the proposed approval and SIP on interstate commerce as significant; such significant burdens outweigh the proposed benefits of the proposed regulation and run afoul of the Dormant Commerce Clause analysis. The compounding costs of testing, certification, and shipping disruption based on the HD I/M Regulation's mandated downtime, and the litany of administrative burdens across State lines, break down the efficiency of interstate trade and would create a de facto national program. 72 As articulated by one commenter, it is hard to properly estimate the ballooning costs of compliance due to the difficulties the program unfairly imposes on out-of-state operators. One commenter estimates that citations for non-compliance may not immediately be received and by the time owners are aware of a citation “potential fines [may reach] up to $10,000 per day depending on the severity and duration of the non-compliance.” Such a risk will lead to fleet closure, alteration, and trade breakdown, none of which was accounted for in CARB's analysis. 73 And contrary to some commenters' assertions, there is no reason to believe that burdens would be lower for out-of-state or out-of-country registered vehicles than for in-state registered vehicles. Notwithstanding the limited exception for 5-day pass throughs discussed elsewhere in this preamble, such owners and operators will generally be forced to over comply, and access to CARB-approved testing and compliance mechanisms and operators is necessarily limited for owners and operators that primarily operate at significant distance from California. As one commenter articulated: “The program's overreach will result in the potential for de facto regulation of out-of-state rented or leased trucks across the country even though renting and leasing companies have no control [over] whether their trucks' routes include traveling into California. . . . CARB's HD I/M program disproportionately affects out-of-state rental and leasing company operations and finances . . . in clear violation of the Dormant Commerce Clause.” 74 72 See generally Comment ID EPA-R09-OAR-2025-0061-0035. 73 See generally Comment ID EPA-R09-OAR-2025-0061-0036. 74 Id. Comment 8: Dormant Commerce Clause—No Significant Burden Several commenters argued that by their nature, the compliance burdens associated with the HD I/M Regulation would not qualify as substantial or undue burdens regardless of the degree of associated benefits. SCAQMD noted that several Supreme Court justices have signaled that Pike balancing of benefits and burdens may be inappropriate in the case of truly nondiscriminatory measures and that, regardless, requirements to keep emission control equipment within the operating parameters required by the HD I/M Regulation should not be considered a significant burden, analogizing it to a requirement for tanker trucks to maintain tanks in leak-free condition to prevent the escape of hazardous materials. An individual commenter questioned how testing for missing and malfunctioning emissions control components that the commenter asserted are already federally required can be considered an undue burden, arguing that drivers who do not want to take the California test can elect not to enter the State. CAELP challenged the EPA's characterization of the HD I/M Regulation's compliance costs as “undoubtedly significant,” arguing that the costs cited are overstated and insufficiently analyzed and do not consider the actual costs to individual operators, calculating that the maximum daily cost to an individual vehicle under the most conservative assumptions would be less than the toll fees assessed by other States. Response: As explained above, in National Pork Producers, “six Justices of [the] Court affirmatively retain[ed] the longstanding Pike balancing test for analyzing Dormant Commerce Clause challenges to state economic regulations.” 75 Under this balancing test, the burdens felt across the nation outweigh the localized benefits to California of more easily discharging its NAAQS attainment obligations under Federal law. The preamble to our proposed rulemaking addresses some of the costs associated with the HD I/M Regulation. Comments from owners and operators in the trucking industry explained that the burdens of applying the HD I/M Regulation to out-of-state and out-of-country registered vehicles will be felt across the entire country. One commenter pointed out that “[b]y nature, trucks are mobile work units that routinely traverse local, state, and international borders. Under the HD I/M program, rented or leased trucks from outside California could potentially enter the state without the knowledge of the rental or leasing company since they are not in control of the vehicles' routes.” 76 Thus, due to compliance costs and the heavy penalties associated with unknowing and incidental violations, out-of-state truckers will be forced to treat California's HD I/M Regulation as a national standard regardless where they concentrate their business. These risks and the attendant burdens are not ameliorated by the HD I/M Regulation's limited pass through exception; rather, the potential for out-of-state and out-of-country registered trucks to apply in advance for a limited “pass through” exemption itself presents burdens, does not comport with the nature of interstate trucking operations, and admits that this aspect of the SIP submission is national in character and unduly burdens truckers in other States and countries who would have to track and amend their routes, dealings, and compliance strategies in the event the program becomes federally enforceable. 75 598 U.S. at 403 (Kavanaugh, J., concurring in part and dissenting in part); see id. at 391 (Sotomayor, J., joined by Kagan, J., concurring in part); id. at 394 (Roberts, C.J., joined by Alito, Kavanaugh, and Jackson, JJ., concurring in part and dissenting in part). 76 Comment ID EPA-R09-OAR-2025-0061-0036. As illustrated by comments, the pass through exemption does not ameliorate these concerns in practice as it requires a prior application replete with information which may not be known to the out-of-state and out-of-country operator in advance, imposes planning and waiting obligations in the form of five business days before the grant of prior permission by the CARB Executive, requires the physical display of the granted pass in the vehicle at all times while operating, and only contemplates a window of five consecutive days per vehicle per year as the maximum allowance, thus making small fleets incapable of using the exemption regularly. Even large fleets could only use each truck in their possession once per year under this program. 77 77 Commenters pointed out that typical truck leases are “dependent on flexible transportation contracts to manage variable operations” and that operators would struggle to plan around this exception, as they typically lack certainty as to if and when a truck would cross into California. Comment ID EPA-R09-OAR-2025-0061-0036. Overcompliance would result to avoid “potential fines reaching up to $10,000 per day.” Id.; see also Comment ID EPA-R09-OAR-2025-0061-0023 (citing the impossibility of compliance); Comment ID EPA-R09-OAR-2025-0061-0016 (a single owner operator would need to buy another truck once the 5-day window was closed). To the extent the HD I/M Regulation applies to out-of-state vehicles that pass through or operate within California for almost any length of time, its cost structure would also be imposed on other States and regulated entities in those States. The EPA notes that many heavy-duty vehicles covered by the regulations at issue are used for purposes of interstate shipping, and that maintenance of those vehicles could occur in any number of States, meaning the burdens of compliance for certain trucking companies to operate in California or merely pass through California will create an economic burden felt throughout the United States. For vehicles merely passing through, the burdens will be felt exclusively by other States. Even for vehicles that intentionally operate within California ( i.e., by shipping goods into the State), these costs may make it prohibitively expensive for certain trucking companies to operate in California, thereby creating an economic rippling effect within and outside the State. “This is particularly burdensome for trucks registered out-of-state, which are considered non-compliant unless they test prior to entering the state. These vehicles might operate in California for only a few hours or days, rather than for weeks or months, but must undergo testing to legally enter the state.” 78 Finally, as explained elsewhere in this preamble, the abstract comparison of benefits and costs in this context should be informed by the nature of the benefits, i.e., allowing California to obtain additional creditable emissions reductions to more easily satisfy its NAAQS-attainment obligations under Federal law. In essence, California is outsourcing the burdens of obtaining this benefit to other States by extending the HD I/M Regulation to out-of-state and out-of-country registered vehicles. That benefit is not a legitimate use of the SIP program, and it does not comport with the balance struck in the CAA between the roles of individual States and the EPA's national role. 78 Comment ID EPA-R09-OAR-2025-0061-0047. Comment 9: Dormant Commerce Clause—Extraterritorial Reach Several commenters challenged the EPA's specific characterizations of extraterritorial effects of the HD I/M Regulation. Some commenters asserted that HD I/M Regulation has no extraterritorial reach or effect that would be relevant to the Commerce Clause analysis. SCAQMD characterized the EPA's position as assuming that any extraterritorial effect is forbidden, which the commenter argues is inconsistent with applicable case law. The commenter cited a Ninth Circuit decision allowing California to ban foie gras produced through force-feeding practices, even though this conduct occurred wholly outside of the State and thus impacted out-of-state conduct. In contrast, the commenter argued, the HD I/M Regulation applies only to conduct within California, does not require actions to be taken outside of California, and has no effect of controlling purely out-of-state actions. Similarly, CCAEJ argued that under applicable case law, the HD I/M Regulation does not violate the Commerce Clause merely based on its extraterritorial reach, arguing that California has authority to apply its laws to non-residents and out-of-state corporate entities. The Coalition for Clean Air (CCA) described the HD I/M Regulation as an exercise by California of the police power held by States to protect their residents and noted that it does not dictate the activities of any other State. CAELP argued that the HD I/M Regulation does not regulate extraterritorially because it does not require compliance from vehicles that do not operate inside of California and does not impose any cost on vehicles when they are outside of California. The commenter analogized the EPA's concerns about the HD I/M Regulation's extraterritorial reach to saying that California could not enforce its criminal laws against residents of other States traveling through California, or that California could not require out-of-state corporations to register before doing business in the State. CARB argued that the HD I/M Regulation does not regulate extraterritorially because it does not directly regulate out-of-state transactions by those with no connection to the State. Response: The Commerce Clause vests the interstate regulatory authority exclusively in Congress. 79 The HD I/M Regulation's extraterritorial application, which would effectively allow California to set a nationwide regulatory standard, as explained in other responses, would represent an abrogation of that unique Federal authority. In addition, the Constitution vests the power over foreign relations exclusively in the Federal Government. The HD I/M Regulation, which applies to all vehicles operating in California, will impermissibly burden vehicles registered in Canada and Mexico and the other States. This is especially pressing in the case of Mexico, which maintains a consulate in California frequented by diplomatic traffic. As explained elsewhere in this preamble, these concerns are heightened by the fact that Congress has legislated on the subject in the CAA by providing that “each State” is responsible for developing a SIP to implement the NAAQS “within” their State, authorizing the EPA to establish national I/M requirements, and allowing for the waiver of Federal preemption only when specific procedural and substantive requirements are met. None of the comments described above presented a valid analogy to the context here, and none can or did substitute for the lack of necessary assurances in California's SIP submission. 79 See Gibbons v. Ogden, 22 U.S. (9 Wheat.) 1 (1824). The EPA disagrees with commenters' assertions that the HD I/M Regulation does not apply extraterritorially. By its terms, the regulatory requirements apply to out-of-state and out-of-country vehicles rather than only in-state registered vehicles, as is generally the case in I/M regimes. This reach was intentional, as California sought to obtain creditable emissions reductions not only from in-state registered vehicles, but also from vehicles registered outside the State. Compliance with the regulatory requirements necessarily contemplates mandating out-of-state and out-of-country conduct, as vehicles must be compliant with the regulation upon entering California or risk substantial penalties. Thus, even before considering that full approval of the SIP submission would make the HD I/M Regulation enforceable outside California against any owner or operator based on allegations that one or more vehicles traversed California, even enforcement within the State of California mandates behavior outside the State. In an illustrative example of the flaws in these commenters' logic, CAELP likens the EPA's concern to “saying California cannot enforce its criminal laws against another state's residents traveling through California or that California . . . cannot require a Delaware corporation to register with the California Secretary of State before transacting business in Los Angeles.” 80 This argument fails to recognize the impact of the EPA's approval of a SIP submission on implementation of the SIP. Because approval makes SIPs federally enforceable, including by citizen plaintiffs, the relevant analogy is not to California enforcing its criminal laws against individuals traversing the State, but to “any person” enforcing California's criminal laws anywhere in the country so long as they allege that an owner or operator's vehicle passed through California at one point in time. 81 The corporate registration analogy is also inapt because the HD I/M Regulation does not contemplate requiring vehicle registration in California as a predicate for being subject to the regulatory requirements. Nor does this comment address the special considerations due to instrumentalities of interstate commerce in the Commerce Clause analysis. 82 Thus, while “the plurality in Pork Producers rejected the argument that any `practical effect' of controlling the conduct of commerce outside the state is barred” 83 it is also true that the HD I/M Regulation, aimed directly at out-of-state instrumentalities—“trucks, trains, and the like” 84 —is likely barred by both Pike and other relevant precedents. 80 Comment ID EPA-R09-OAR-2025-0061-0043. 81 See CAA sections 304(a) (authorizing “any person” to commence a civil action for alleged violations), 302(e) (defining “person” as any “individual, corporation, partnership, association, State, municipality, political subdivision of a State” as well as any arm of the Federal Government). 82 The case law cited by SCAQMD is equally inapplicable here. Association des Eleveurs de Canard et d'Oies du Quebec v. Bonta, 33 F.4th 1107, 1118 (9th Cir. 2022), dealt with a State law banning the practice of selling foie gras products in the State of California. The Ninth Circuit dismissed claims asserting a variety of Commerce Clause and preemption arguments because, in that instance, the State law pertained only to what could be sold within California. Thus, that case pertained to the regulation of in-state sales and did not involve instrumentalities of interstate commerce. Additionally, Rocky Mountain Farmers Union v. Corey, 730 F.3d 1070, 1103 (9th Cir. 2013), pertained to the impact of the State's ethanol standards based on the full lifecycle of the production of ethanol fuels. The Ninth Circuit found the law nondiscriminatory despite its practical impact on out-of-state fuel production and remanded for analysis under the Pike balancing test. Thus, this analysis does not pertain to instrumentalities of commerce or the burdens a federally empowered SIP would produce on out-of-state parties. 83 Comment ID EPA-R09-OAR-2025-0061-0043. 84 Nat'l Pork Producers, 598 U.S. at 379-80 & n.2 (majority op.) These commenters acknowledge that restrictions upon the instrumentalities of commerce—like trucks—fall under the purview of the Commerce Clause. And as emphasized above, regardless of the existence of discriminatory intent, such restrictions upon instrumentalities of commerce implicate special considerations in the Commerce Clause analysis. As explained in the response to Comment 11, the HD I/M Regulation also “expresses a distinct point of view” on the politically charged issue of vehicle emissions reductions in vehicles registered in and operating outside California and outside the United States. This implicates the foreign affairs powers vested exclusively in the Federal Government. 85 85 United States v. Pink, 315 U.S. 203, 233, (1942) (“Power over external affairs is not shared by the States; it is vested in the national government exclusively.”). Comment 10: Dormant Commerce Clause—Special Rules for Instrumentalities of Interstate Transportation SCAQMD acknowledged recent case law indicating that the Commerce Clause applies with special force to regulations affecting “instrumentalities of interstate transportation,” but suggested that relevant cases involved regulations that either had no benefit or conflicted with requirements in other States. 86 Similarly, CARB cited case law suggesting that courts have invalidated facially neutral State regulations on instrumentalities of interstate transportation only when they were enacted at the instance of, and primarily benefit, in-state interests. The commenters argued that these cases would not support invalidating the HD I/M Regulation. 86 See generally Comment ID EPA-R09-OAR-2025-0061-0039, which cites to Bibb v. Navajo Freight Lines, 369 U.S. 520 (1959), Kassel v. Consolidated Freightways Corp. of Delaware, 450 U.S. 662 (1981), and Raymond Motor Transportation, Inc., v. Rice, 434 U.S. 429 (1978), as examples of such cases. Commenter seeks to limit the Pike test to circumstances like those in these cases in which the invalidated State law had no major benefits to the local State. But that is not what these cases say. Rather, they highlight the special scrutiny applied to instrumentalities of interstate commerce like heavy duty trucking. And in each instance, the State law was invalidated despite involving arguably lower burdens than the HD I/M Regulation at issue here. Conversely, another commenter articulated: “The program's overreach will result in the potential for de facto regulation of out-of-state rented or leased trucks across the country even though renting and leasing companies have no control [over] whether their trucks' routes include traveling into California. Since CARB's HD I/M program disproportionately affects out-of-state rental and leasing company operations and finances, the program . . . [is] in clear violation of the Dormant Commerce Clause.” 87 87 Comment ID EPA-R09-OAR-2025-0061-0036. Response: The Supreme Court noted in National Pork Producers that “there exists a strong line of cases that originated before Pike in which th[e] Court refused to enforce certain state regulations on instrumentalities of interstate transportation—trucks, trains, and the like.” 88 These cases and others demonstrate that State laws that burden “instrumentalities of interstate transportation” warrant special consideration under the Commerce Clause and may be invalid even in the absence of discriminatory intent. Commenters did not offer a plausible explanation that the HD I/M Regulation does not squarely implicate this line of cases, or that California must be excused from providing “necessary assurances” that implementing its SIP submittal to out-of-state and out-of-country registered vehicles would not run afoul of applicable law. 88 598 U.S. at 379 n.2; see, e.g., Bibb, 359 U.S. at 523-30 (concerning a State law specifying certain mud flaps for trucks and trailers); S. Pac. Co., 325 U.S. at 763-82 (addressing a State law regarding the length of trains). Contrary to these commenters' suggestions, full approval of the HD I/M Regulation would necessarily generate conflict with I/M regimes adopted in other States, including both existing programs and programs that other States may seek to incorporate into their SIPs to obtain creditable emissions reductions in the future. If made federally enforceable by approval, “any person” could seek to enforce the HD I/M Regulation by alleging a vehicle passed through California without first complying with the regulation's requirements. As noted above, this would create multiple and conflicting obligations with any State that adopts a different I/M program and improperly pressure other States to adopt an identical program into their SIP, with attendant difficulties in disaggregating which emissions reductions could properly be attributed to which State. Furthermore, the EPA disagrees with commenters' assertions that the HD I/M Regulation involves local benefits that distinguish a potential approval from the State laws at issue in the cited cases. Here, the benefits adhere purely to California by allowing the State to obtain credit for additional emissions reductions beyond those that could be credited by applying the HD I/M Regulation to in-state registered vehicles. Those benefits are purely local, and they are not the type of direct local benefits that courts have previously recognized as legitimate ends. Nor are commenters correct that courts have taken issue with State regulations burdening interstate commerce only when there were no local benefits. Rather, the line of cases discussed above recognizes the centrality of instrumentalities of interstate commerce to the national market envisioned by the Commerce Clause and that local benefits are more difficult to justify in the face of burdening such instrumentalities. Comment 11: Foreign Relations Powers Several commenters challenged the EPA's proposed basis for partial disapproval related to concerns that extraterritorial reach of the HD I/M Regulation violates the foreign relation powers vested exclusively in the Federal Government by the U.S. Constitution. SCAQMD argued that the HD I/M Regulation does not have a prohibited effect on foreign commerce, stating that there is no evidence of discrimination or protectionism, and that California does not seek to provide an advantage for in-state trucks. In response to the EPA's concerns that HD I/M Regulation does not have an exception for diplomatic activities by foreign nationals, the commenter argued that such an exemption is unnecessary because diplomatic immunity is afforded by Federal law external to the CAA or State regulations. The commenter stated that cases interpreting “dormant” aspects of the Foreign Commerce Clause focus on taxes and fees imposed on instrumentalities of international commerce with legal tests that do not apply in this case. The commenter argued that the HD I/M Regulation does not violate the Foreign Commerce Clause as described in these cases because it does not adversely impact the Federal Government's ability to speak with one voice. CCAEJ argued that the EPA has not identified or considered any international treaties or conventions that would bear on California's authority to adopt operational limitations on mobile sources under the CAA. The commenter stated that the EPA failed to consider in particular the United States-Mexico-Canada Agreement (USMCA), arguing that California would retain its CAA authority to adopt the HD I/M Regulation under provisions of the Agreement specifying that the environmental law of the United States continues to apply. The commenter included portions of the USMCA language as an attachment. CAELP argued that the HD I/M Regulation comports with the foreign affairs doctrine, arguing that HD I/M Regulation does not impinge upon the Federal Government's conduct of foreign affairs. The commenter disputed the EPA's characterization of potential conflicts with foreign affairs authorities, arguing that the EPA's position would mean that the Federal Government could block any State policy that it disfavored simply because it might have some marginal effect on foreign entities. According to the commenter, the Supreme Court has rejected this view, finding a violation only where there is a direct impact on foreign relations that could adversely affect the Federal Government's power to deal with relevant problems. The commenter suggested that the EPA's position could also raise separation of powers concerns to the extent it intrudes into Congress' role in establishing the boundaries for States' exercise of personal jurisdiction. The commenter stated that the HD I/M Regulation is not expressly preempted because it does not conflict with any treaties, conventions, executive agreements, or express foreign policies. The commenter further stated that it is not field preempted because it does not intrude on the Federal Government's foreign affairs power under Ninth Circuit case law, because the EPA has not offered any evidence that HD I/M Regulation diminishes the President's power to speak and bargain effectively with other countries, and because it addresses a traditional State responsibility and is not intended to influence policy in other countries. CARB argued that the EPA has not provided a reasoned basis for partial disapproval related to foreign affairs preemption because it does not cite any treaties or conventions or any potential impacts on relevant Federal policy and because courts recognize conflict preemption only in the face of a clear and definite foreign policy. The commenter noted that the CAA relaxes State planning obligations in areas affected by pollution from foreign countries but does not distinguish State obligations to address emissions based on the nationality of emissions sources. The commenter also argued that the HD I/M Regulation does not unlawfully regulate in the field of foreign affairs because it addresses a traditional State responsibility. The commenter further argued that the HD I/M Regulation does not intrude on the Federal Government's foreign [Text truncated at 120,000 characters. The full text is on the page linked above.] --- Source: Frix Law Library, https://www.frixlaw.com/law-library/documents/fr%3A2026-02350. Public record. Not legal advice.