Natural Resources Defense Council v. Andrew Wheeler

United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued May 3, 2019 Decided April 7, 2020

No. 18-1172

NATURAL RESOURCES DEFENSE COUNCIL,

PETITIONER

v.

ANDREW WHEELER, ADMINISTRATOR, U.S. ENVIRONMENTAL

PROTECTION AGENCY AND ENVIRONMENTAL PROTECTION

AGENCY,

RESPONDENTS

ARKEMA INC. AND MEXICHEM FLUOR, INC.,

INTERVENORS

Consolidated with 18-1174

On Petitions for Review of an Action of the

United States Environmental Protection Agency

Peter J. DeMarco argued the cause for petitioner Natural

Resources Defense Council. With him on the briefs were

Melissa J. Lynch and David D. Doniger.

2

Joshua M. Tallent, Assistant Attorney General, Office of the

Attorney General for the State of New York, argued the cause

for State Petitioners. With him on the briefs were

Letitia James, Attorney General, Barbara D. Underwood,

Solicitor General, Steven C. Wu, Deputy Solicitor General,

Michael J. Myers, Senior Counsel, and Morgan A. Costello,

Chief, Office of the Attorney General for the State of New

York; Kwame Raoul, Attorney General, and Daniel I.

Rottenberg, Assistant Attorney General, Office of the Attorney

General for the State of Illinois; Xavier Becerra, Attorney

General, David A. Zonana, Supervising Deputy Attorney

General, and Megan K. Hey, Deputy Attorney General, Office

of the Attorney General for the State of California; Maura

Healey, Attorney General, Christophe G. Courchesne,

Assistant Attorney General, and Megan M. Herzog, Special

Assistant Attorney General, Office of the Attorney General for

the Commonwealth of Massachusetts; Ellen F. Rosenblum,

Attorney General, and Paul A. Garrahan, Attorney-in-Charge,

Office of the Attorney General for the State of Oregon;

Kathleen Jennings, Attorney General, and Valerie M. Edge,

Deputy Attorney General, Office of the Attorney General for

the State of Delaware; Keith Ellison, Attorney General, and

Max H. Kieley, Assistant Attorney General, Office of the

Attorney General for the State of Minnesota; Robert A. Reiley,

Assistant Counsel, Commonwealth of Pennsylvania

Department of Environmental Protection; Karl A. Racine,

Attorney General, and Loren L. AliKhan, Solicitor General,

Office of the Attorney General for the District of Columbia;

Gurbir S. Grewal, Attorney General, and Lisa J. Morelli,

Deputy Attorney General, Office of the Attorney General for

the State of New Jersey; Thomas J. Donovan, Jr., Attorney

General, and Nicholas F. Persampieri, Assistant Attorney

General, Office of the Attorney General for the State of

Vermont; Robert W. Ferguson, Attorney General, and

3

Katharine G. Shirey, Assistant Attorney General, Office of the

Attorney General for the State of Washington.

Benjamin Carlisle, Attorney, U.S. Department of Justice,

argued the cause for respondent. With him on the brief were

Jeffrey Bossert Clark, Assistant Attorney General, Jonathan

Brightbill, Deputy Assistant Attorney General, and Jan M.

Tierney and Diane E. McConkey, Attorneys, U.S.

Environmental Protection Agency.

Keith Bradley argued the cause for intervenors. With him

on the brief were W. Caffey Norman, Dan Himmelfarb, John S.

Hahn, Roger W. Patrick, and William J. Hamel.

Before: SRINIVASAN , Chief Judge, and TATEL and RAO,

Circuit Judges.

Opinion for the Court filed by Chief Judge SRINIVASAN .

Dissenting opinion filed by Circuit Judge RAO.

SRINIVASAN, Chief Judge: Thirty years ago, Congress

amended the Clean Air Act to require that users of ozone-

depleting substances transition to use of less harmful

substitutes. Many users replaced ozone-depleting substances

with hydrofluorocarbons (HFCs). Over time, though, scientists

came to understand that HFCs, while not ozone-depleting

substances, are powerful greenhouse gases that contribute to

climate change.

In 2015, EPA issued a regulation disallowing the use of

HFCs as a substitute for ozone-depleting substances. That rule

was challenged in our court in Mexichem Fluor, Inc. v. EPA,

866 F.3d 451 (D.C. Cir. 2017). We determined that EPA could

validly forbid current users of ozone-depleting substances from

4

switching to HFCs. But we also concluded that EPA lacked

authority to force users who had already switched to HFCs to

make a second switch to a different substitute. We thus vacated

the rule in part and remanded to the agency.

On remand, even though we had sustained EPA’s bar

against use of HFCs with regard to entities who were still using

ozone-depleting substances, the agency decided to implement

our decision by suspending the rule’s listing of HFCs as unsafe

substitutes in its entirety, meaning that even current users of

ozone-depleting substances can now shift to HFCs. And EPA

did so without going through notice-and-comment procedures.

The Natural Resources Defense Council and a group of

states have now filed petitions for review in our court. They

argue among other things that EPA’s rule on remand

improperly amended the agency’s earlier rule without adhering

to notice-and-comment procedures. We agree, and we

therefore grant the petitions for review and vacate the

challenged rule.

I.

In the 1970s, scientists realized that some chemicals used

by humans deplete the layer of ozone gas above the Earth’s

surface that protects humans from ultraviolet radiation’s

harmful effects. See Nat. Res. Def. Council v. EPA, 464 F.3d

1, 3 (D.C. Cir. 2006). Based on those concerns, the United

States and other countries, in the late 1980s, developed the

Montreal Protocol on Substances that Deplete the Ozone

Layer, Sept. 16, 1987, S. Treaty Doc. No. 100–10, 1522

U.N.T.S. 29. The Protocol is an international agreement

requiring signatories to regulate ozone-depleting substances.

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In 1990, Congress implemented the United States’

obligations under that agreement by adding to the Clean Air

Act a new Title VI, 42 U.S.C. § 7671 et seq. Title VI requires

that, “[t]o the maximum extent practicable,” ozone-depleting

substances “be replaced by chemicals, product substitutes, or

alternative manufacturing processes that reduce overall risks to

human health and the environment.” Id. § 7671k(a). And to

help guard against the replacement of ozone-depleting

substances with alternatives that are themselves harmful, the

statute directs EPA to promulgate rules making it unlawful to

replace ozone-depleting substances with substances that “may

present adverse effects to human health or the environment.”

Id. § 7671k(c). To that end, EPA must maintain lists of

“prohibited” and “safe” substitutes for specific uses. Id.

EPA has promulgated a number of regulations approving

or prohibiting various substitutes for certain end-uses. See,

e.g., Protection of Stratospheric Ozone: Listing of Substitutes

for Ozone-Depleting Substances, 68 Fed. Reg. 4004 (Jan. 27,

2003); Protection of Stratospheric Ozone, 59 Fed. Reg. 13,044

(Mar. 18, 1994). One group of substitutes addressed in many

of those regulations is hydrofluorocarbons (HFCs), a family of

“substances that contain hydrogen, fluorine, and carbon.”

Mexichem, 866 F.3d at 455. In 1994, EPA “concluded that

certain HFCs were safe substitutes for ozone-depleting

substances when used in aerosols, motor vehicle air

conditioners, commercial refrigerators, and foams, among

other things.” Id. Over the following decade, EPA “added

HFCs to the list of safe substitutes for a number of other

products.” Id. Throughout the 1990s and 2000s, as businesses

transitioned away from ozone-depleting substances, they often

employed HFCs as a substitute. See id.

But over time, EPA became increasingly concerned about

HFCs. Although HFCs are not ozone-depleting substances,

6

they are powerful greenhouse gases that, in EPA’s view, “may

contribute to climate change, increasing the incidence of

mortality and the likelihood of extreme weather events such as

floods and hurricanes.” Id. In 2015, after going through

notice-and-comment procedures, EPA promulgated a rule

moving some HFCs from the safe substitutes list to the

prohibited substitutes list. See Protection of Stratospheric

Ozone: Change of Listing Status for Certain Substitutes Under

the Significant New Alternatives Policy Program, 80 Fed. Reg.

42,870 (July 20, 2015). The 2015 Rule prohibited current users

of ozone-depleting substances from replacing those substances

with HFCs. But the Rule also went further, prohibiting the

continued use of certain HFCs by users who had already

switched from ozone-depleting substances to HFCs. See

Mexichem, 866 F.3d at 456.

The latter measure proved too ambitious. In Mexichem,

we determined that EPA’s attempt to regulate users who had

already switched from ozone-depleting substances to HFCs

exceeded the agency’s statutory authority. Title VI, we

concluded, only “makes it unlawful to ‘replace’ an ozone-

depleting substance that is covered . . . with a substitute

substance that is on the list of prohibited substitutes.” Id. at

458 (quoting 42 U.S.C. § 7671k(c)). And businesses “‘replace’

an ozone-depleting substance when they transition to making

[or using] the same product with a substitute substance. After

that transition has occurred, the replacement has been

effectuated,” and there is no longer an “ozone-depleting

substance to ‘replace.’” Id. at 459. And because HFCs are not

ozone-depleting substances, we concluded that once an entity

replaces ozone-depleting substances with HFCs, its HFC use is

no longer regulated by Title VI. In that situation, we held, EPA

lacks authority to require a second substitution in place of

HFCs. See id.

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At the same time, with regard to EPA’s decision to move

HFCs to the list of prohibited substitutes on a going-forward

basis, we reaffirmed that the agency may “move a substitute

from the list of safe substitutes to the list of prohibited

substitutes” and “may prohibit a manufacturer [or other

regulated entity] from replacing an ozone-depleting substance

that is covered under Title VI with a prohibited substitute.” Id.

at 457. We also rejected the petitioners’ myriad arbitrary-and-

capricious challenges, holding that “EPA reasonably removed

HFCs from the list of safe substitutes.” Id. at 462–63. For

those reasons, we granted the petitions for review of the 2015

Rule “in part,” by vacating the 2015 Rule only “to the extent it

requires manufacturers to replace HFCs with a substitute

substance.” Id. at 464.

Eight months later, in April 2018, EPA published in the

Federal Register a rule explaining its “response to the court’s

decision.” See Protection of Stratospheric Ozone: Notification

of Guidance and a Stakeholder Meeting Concerning the

Significant New Alternatives Policy (SNAP) Program, 83 Fed.

Reg. 18,431, 18,432 (Apr. 27, 2018). EPA issued the 2018

Rule without going through notice-and-comment procedures.

Although EPA recognized that Mexichem effected only a

“partial vacatur of the 2015 Rule,” the agency determined that

it would “not apply the HFC use restrictions or unacceptability

listings in the 2015 Rule for any purpose prior to completion”

of an anticipated future rulemaking on the subject. Id. at

18,433 (italics omitted). EPA’s decision to stop applying the

HFC restrictions in their entirety, rather than only with respect

to users who had already switched to HFCs (as Mexichem had

contemplated), rested primarily on two bases.

First, EPA explained that the “regulatory text promulgated

in the 2015 Rule” had consisted of “individual listing

decisions” that prohibited or restricted the use of a given HFC

8

in a given end-use, without regard to the distinction drawn in

Mexichem between users who had already switched to HFCs

and users still using ozone-depleting substances. Id. at 18,434.

“[F]or each listing decision,” EPA reasoned, “there is no

language that could be understood as being removed or struck

out by the court so that some portion of the listing would

remain in effect pending EPA’s action on remand.” Id.

Second, EPA determined that “attempting to draw the

distinctions made by the court would present practical

difficulties for implementation.” Id. For example, the agency

posited, there could be “complex situations” in which a

regulated entity uses ozone-depleting substances in some

facilities and HFCs in other facilities, such that it would be

unclear whether the entity had already “replaced” ozone-

depleting substances with HFCs. Id. at 18,435.

In sum, EPA “recognize[d] that the court” in Mexichem

had “vacated the 2015 Rule ‘to the extent that’ it requires

manufacturers to replace HFCs.” Id. But given “its expertise

in administering the [relevant] regulations, and its

understanding of the 2015 Rule, EPA conclude[d] that the

vacatur [could not] be implemented” in the way contemplated

by our decision in Mexichem. Id. EPA instead decided to

“treat[]” the vacatur “as striking the HFC listing changes in the

2015 Rule in their entirety.” Id. And the agency thus

determined that it “will not apply the HFC use restrictions or

unacceptability listings in the 2015 Rule for any purpose.” Id.

EPA also announced that it was “prepar[ing] to undertake

notice-and-comment rulemaking” to address various issues

related to Mexichem, HFCs, and the safe substitutes program

more generally. Id. at 18,435–36.

Following publication of that 2018 Rule, both the Natural

Resources Defense Council and a group of states filed petitions

for review of EPA’s action in our court, which we consolidated.

9

Petitioners contend that the 2018 Rule is invalid, both because

EPA improperly issued it without adhering to notice-and-

comment procedures and because it is substantively arbitrary

and capricious. In response, two intervenors (HFC

manufacturers Arkema Inc. and Mexichem Fluor, Inc.) argue

that we lack jurisdiction over the petitions for review because

petitioners fail to demonstrate their standing to seek relief. In

addition, the intervenors and EPA contend that we lack

jurisdiction because the 2018 Rule is not final agency action,

and they also defend the Rule on the merits.

II.

A.

We begin by considering petitioners’ standing. Because

Article III of the Constitution limits us to “resolving cases and

controversies, a showing of standing is an essential and

unchanging predicate to any exercise of our jurisdiction.” Nat.

Res. Def. Council v. EPA, 755 F.3d 1010, 1016 (D.C. Cir.

2014) (internal quotation marks omitted). To establish

standing, a party must demonstrate: “(1) an injury in fact that

is concrete and particularized as well as actual or imminent; (2)

a causal connection between the injury and the challenged

conduct; and (3) a likelihood, as opposed to mere speculation,

that the injury will be redressed by a favorable decision.” Id.

(internal quotation marks omitted). In addition, when a

representational organization like NRDC sues on behalf of its

members, it must also show that (1) “its members would

otherwise have standing to sue in their own right”; (2) “the

interests it seeks to protect are germane to the organization’s

purpose”; and (3) “neither the claim asserted nor the relief

requested requires the participation of individual members.”

Id. (citation omitted).

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Here, NRDC and at least one of the state petitioners have

satisfied their burden to show an injury both caused by the 2018

Rule and likely to be redressed by a favorable decision. To link

the 2018 Rule to an injury-in-fact, petitioners begin with the

contention that the 2018 Rule, by vacating the entirety of the

2015 Rule’s HFC listings, allows entities to switch from ozone-

depleting substances to HFCs and thus will cause an increase

in HFC emissions. While EPA does not contest that premise,

intervenors do. They argue that the 2018 Rule will not cause

any such increase because it is our decision in Mexichem, as

opposed to the 2018 Rule, that “effectively undid the” 2015

Rule. See Intervenors Br. 27–28.

But, as is discussed below, petitioners’ core contention in

this case is that Mexichem only partially vacated the 2015 Rule,

and that the 2018 Rule then had an independent legal effect by

vacating the rest of the HFC listings in the 2015 Rule. And for

purposes of determining standing, we must assume that

petitioners will prevail on the merits of their argument. See

Defs. of Wildlife v. Gutierrez, 532 F.3d 913, 924 (D.C. Cir.

2008). We thus assume that petitioners are correct that the

2018 Rule, and not Mexichem, completed the vacatur of the

2015 Rule’s HFC listings. And no party disputes petitioners’

contention that allowing additional entities to use HFCs will in

fact lead to additional use of HFCs.

Once we accept the premise that the 2018 Rule will lead

to an increase in HFC emissions, the rest of the standing

analysis falls readily into place. As the parties agree, the

release of HFCs contributes to climate change. And NRDC has

submitted a declaration from a member averring that he owns

coastal property in New Jersey that is especially vulnerable to

weather events caused or worsened by climate change, and

New York state similarly demonstrated its proprietary interest

in coastal lands threatened by climate change. See NRDC Br.

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S.A. 13–19; States Br. 23–24; Snyder Decl. ¶ 30; cf.

Massachusetts v. EPA, 549 U.S. 497, 519 (2007). Petitioners

then have adequately linked the 2018 Rule to an injury-in-fact:

the 2018 Rule will lead to an increase in HFC emissions, which

will in turn lead to an increase in climate change, which will

threaten petitioners’ coastal property. And of course, a vacatur

of the 2018 Rule would redress that injury by restoring the

2015 Rule’s HFC listings as applied to those entities that

Mexichem found EPA could validly regulate, thereby reducing

HFC emissions.

It follows that both NRDC and New York have established

the injury, causation, and redressability requirements of

standing, and New York has shown its standing. (Because New

York has demonstrated its standing, we need not address the

standing of the other state petitioners. See Massachusetts, 549

U.S. at 518). As noted above, however, NRDC must clear two

additional hurdles to establish standing to bring its own

separate petition because it is suing in a representational

capacity: NRDC must show that its petition is germane to its

purpose and that the claims asserted or relief sought do not

require the involvement of its individual members.

NRDC satisfies both of those requirements. As NRDC

explains in its brief, it is an environmental organization that is

“committed to reducing emissions of greenhouse gases” and

that has long “worked on multiple fronts to reduce HFC

pollution.” NRDC Br. 15–16; cf. Nat. Res. Def. Council, 755

F.3d at 1016 (allowing NRDC to proceed in a representational

capacity in an environmental lawsuit). And NRDC neither

seeks any individualized relief nor brings claims dependent on

any individual member’s factual circumstances, which means

that no individual member’s participation is necessary to its

petition. We therefore find that NRDC, like New York, has

established its standing to proceed.

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B.

We next consider whether the 2018 Rule amounts to final

agency action subject to judicial review. The Clean Air Act

provides for judicial review only of “final action,” 42 U.S.C.

§ 7607(b)(1), a limitation coterminous with the concept of

“final agency action” in the Administrative Procedure Act, 5

U.S.C. § 704. See Sierra Club v. EPA, 873 F.3d 946, 951 (D.C.

Cir. 2017). An action is “final if two independent conditions

are met: (1) the action ‘marks the consummation of the

agency’s decisionmaking process’ and is not ‘of a merely

tentative or interlocutory nature;’ and (2) it is an action ‘by

which rights or obligations have been determined, or from

which legal consequences will flow.’” Soundboard Ass’n v.

Fed. Trade Comm’n, 888 F.3d 1261, 1267 (D.C. Cir. 2018)

(alteration omitted) (quoting Bennett v. Spear, 520 U.S. 154,

177–78 (1997)). The 2018 Rule satisfies both of those criteria.

1.

The 2018 Rule represents the consummation of EPA’s

decisionmaking process. Neither EPA nor intervenors contend

otherwise, and for good reason.

The consummation prong of the finality inquiry requires

us to determine “whether an action is properly attributable to

the agency itself and represents the culmination of that

agency’s consideration of an issue,” or is, instead, “only the

ruling of a subordinate official, or tentative.” Id. (citation

omitted); see id. at 1269 (analyzing whether agency action is

“subject to further agency review” (citation omitted)). Here,

the 2018 Rule was issued under the authority of the

Administrator himself, was published in the Federal Register,

and was the culmination of EPA’s consideration of the issue of

how to treat the 2015 Rule’s HFC listings pending any further

13

formal rulemaking. The 2018 Rule thus is far removed from

the types of agency action—such as informal letters issued by

subordinate officials—that we have held do not amount to the

culmination of an agency’s decisionmaking process. See id. at

1267–68.

The 2018 Rule marks the culmination of EPA’s

decisionmaking for finality purposes notwithstanding the

agency’s characterization of the Rule as an interim resolution:

EPA has stated its intention to commence another rulemaking

that will address the use of HFCs as replacements for ozone-

depleting substances on a permanent basis, and the outcome of

such a process could displace the 2018 Rule going forward.

See 83 Fed. Reg. at 18,435–36. But even if the 2018 Rule were

to be displaced by another rule at some point, our precedents

make clear that an interim agency resolution counts as final

agency action despite the potential for a different permanent

decision, as long as the interim decision is not itself subject to

further consideration by the agency. In that event, the interim

resolution is the final word from the agency on what will

happen up to the time of any different permanent decision.

For example, in Clean Air Council v. Pruitt, 862 F.3d 1

(D.C. Cir. 2017) (per curiam), we held that a stay of a

regulation pending the resolution of a petition for

reconsideration of the regulation qualified as final action: “In

effect, the Administrator has granted a modification of the

mandatory [regulation] for the entire period of time that the

petition is pending. There is no indication that the

[Administrator] intends to reconsider this decision or to vacate

the grant of interim relief. Thus, the [Administrator’s] decision

represents the final agency position on this issue . . . .” Id. at 6

(citation omitted). Similarly, in International Union, United

Mine Workers of America v. Mine Safety & Health

Administration, 823 F.2d 608 (D.C. Cir. 1987), we held that we

14

had jurisdiction over a petition for review of the MHSA’s

decision to grant a mine operator interim relief from a safety

standard pending resolution of the operator’s petition for

permanent modification of the standard. In that case too, we

determined that the grant of relief was “final” notwithstanding

its interim nature because there was “no indication that the

Secretary intends to reconsider . . . or to vacate the grant of

interim relief.” Id. at 614–15.

Here, the 2018 Rule is even more final than were the

interim decisions in Clean Air Council and International

Union. In those cases, a proceeding that could result in an

alteration of the interim resolution—a petition for

reconsideration in Clean Air Council, and a petition for

permanent modification in International Union—had already

been commenced. Here, by contrast, EPA has indicated that it

intends to undertake a further rulemaking at some point but has

not formally initiated the process. And even if EPA in the

future were to do so and were to promulgate a new rule

addressing the treatment of HFCs under Title VI, the 2018 Rule

firmly establishes EPA’s current position that the 2015 Rule’s

HFC listings are unenforceable, and that position will continue

to govern unless and until the agency issues a new rule. That

counts as consummation of agency decisionmaking for finality

purposes.

A contrary conclusion would be incompatible with our

usual practice when an agency informs us that it wishes to

reconsider a rule that is the subject of a pending petition for

review before our court. In such a circumstance, we face a

choice between remanding to the agency or continuing with our

review. See Utility Solid Waste Activities Grp. v. EPA, 901

F.3d 414, 436–38 (D.C. Cir. 2018). But if the prospect of an

agency’s reconsideration of a rule sufficed to render the rule

non-final, then when an agency tells us it wants to reconsider a

15

rule that is before us on review, we could neither remand to the

agency nor continue our review. Instead, we would be

compelled to dismiss for lack of jurisdiction, which we have

never done (or thought it necessary to do) in that situation.

Additionally, if an agency’s indication of an intent to

reconsider an interim (or other) action sufficed to render the

action non-final, agencies could evade judicial review of their

actions even if they impose substantial obligations on regulated

parties over a considerable period of time. Consider, in that

regard, a recent case in our court, Exhaustless v. FAA, 931 F.3d

1209 (2019). That case involved the Federal Aviation

Administration’s regulation of take-off and landing slots at

LaGuardia and John F. Kennedy Airports. Id. at 1210. In 2006

(for LaGuardia) and 2008 (for Kennedy), the FAA published

“interim” regulations governing distribution of those slots

ostensibly for a limited time, and professed an intent to finalize

a permanent rule in the near future. Id. at 1210–12. More than

a decade later, however, those “interim” regulations have been

extended multiple times and remain in effect. Id. It would

make little sense to deem such “interim” rules non-final—and

hence non-challengeable—merely because of the prospect that

they could be displaced at some point by further agency action.

Here, for instance, assuming that EPA has a good-faith

intent to engage in a rulemaking that will settle the treatment

of HFCs on an ostensibly permanent basis, it is wholly

uncertain what the resulting regime will look like or when it

will be in place. It could take the agency considerable time to

gather the necessary input and settle on a solution. And for all

we know, at the end of that process, EPA might even come to

the conclusion that the 2018 Rule already embodies the proper

resolution of the issue (or it could reach any of an unknown

number of other potential solutions). Regardless, until then,

EPA will continue to apply the 2018 Rule. That Rule marks

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the consummation of the agency’s decisionmaking about the

governing framework unless and until it is superseded.

Finally, any agency action is always subject to

displacement by a future rulemaking. If the mere possibility of

displacement rendered a governing agency rule non-final for

purposes of judicial review, no rule would ever count as final.

Our precedents understandably prescribe a contrary approach,

under which, as long as an agency has completed its

decisionmaking on a challenged rule—even one interim in

nature—the rule satisfies the first prong of the finality test. See

Clean Air Council, 862 F.3d at 6; Int’l Union, 823 F.2d at 614–

15. It follows that, as both EPA and petitioners agree, the 2018

Rule marks the consummation of the agency’s decisionmaking

process.

2.

The 2018 Rule also determined legal rights and obligations

and gave rise to legal consequences for purposes of the second

prong of the finality test. As we have recognized, an agency’s

suspension of regulatory requirements ordinarily “affects

regulated parties’ rights or obligations.” Clean Air Council,

862 F.3d at 7 (internal quotation marks omitted). Here, no

party disputes that, to the extent the 2018 Rule suspends the

2015 Rule’s HFC listings, the 2018 Rule determines legal

rights and obligations and carries legal consequences by giving

regulated parties the legal right to replace ozone-depleting

substances with HFCs.

EPA and intervenors, though, contend that the 2018 Rule

does not determine legal rights and obligations or effect legal

consequences. In their view, it was our decision in Mexichem,

not the 2018 Rule, that suspended the 2015 Rule’s HFC

listings. According to that account, the 2018 Rule “simply

17

applies and implements” Mexichem and “therefore has no

independent legal consequences.” EPA Br. 19. That is

incorrect.

Our decision in Mexichem makes clear that it did not

vacate the HFC listings in the 2015 Rule in their entirety. The

decision rested on an understanding of EPA’s statutory

authority to regulate entities’ replacement of ozone-depleting

substances. We reasoned that an entity “replaces” an ozone-

depleting substance when it switches to a substitute substance,

and that EPA’s statutory authority thus extends only to

regulating the initial switch. See 866 F.3d at 458–59. And

because HFCs are not themselves ozone-depleting substances,

we concluded, EPA had no statutory authority to compel an

entity already using HFCs to replace them with alternate

substitutes. See id. We thus held that EPA cannot permissibly

apply the 2015 Rule’s HFC listings to entities already using

HFCs. Id. We made no suggestion, though, that EPA cannot

apply the 2015 Rule to entities still using ozone-depleting

substances. Our decision accordingly did not vacate the 2015

Rule’s HFC listings in toto.

To the contrary, the Mexichem decision repeatedly evinced

our understanding that we were vacating the HFC listings only

in part. Four distinct times, we emphasized that we were

vacating the 2015 Rule only “to the extent” the Rule requires

replacements of HFCs, id. at 454, 462, 464, confirming that we

otherwise sought to leave the HFC listings intact. Similarly,

when discussing EPA’s theory that it could apply the 2015 Rule

to all parties that had previously used ozone-depleting

substances but had since switched to HFCs, we explained that

the agency had not met the necessary requirements to allow

retroactive rulemaking and that, “[u]nless and until” it did so,

“EPA may not apply the 2015 Rule to require manufacturers to

replace one non-ozone-depleting substitute with another

18

substitute.” Id. at 462. Again, the straightforward implication

of our statement is that EPA may apply the 2015 Rule in other

circumstances.

We echoed the same understanding when, after concluding

that EPA lacked statutory authority to apply the 2015 Rule’s

listings to entities that had already switched to HFCs, we went

on to consider—and reject—the manufacturers’ various

arguments that “EPA’s decision to remove HFCs from the list

of safe substitutes was arbitrary and capricious.” Id. at 462–

63. That entire discussion would have been wholly

unnecessary had we believed that the first part of our opinion

(about EPA’s statutory authority) meant we were vacating the

2015 HFC listings in their entirety.

In short, our decision in Mexichem reinforced throughout

an intention only to forbid EPA from applying the 2015 Rule’s

HFC listings to a discrete set of regulated parties (those that

had already switched from ozone-depleting substances to

HFCs), not to set aside the 2015 Rule’s HFC listings in their

entirety. The 2018 Rule goes further than Mexichem by

instituting a complete vacatur of the 2015 Rule’s HFC listings.

And vacating those listings has the effect of suspending

regulatory requirements, which qualifies as determining legal

rights or obligations and carrying legal consequences for

purposes of the second finality prong.

EPA and intervenors contend that the 2018 Rule

nonetheless has no independent legal effect because “the aspect

of the 2015 Rule that exceeded EPA’s authority” per Mexichem

“flow[s] from the exact same regulatory text” as “the aspect

that did not.” EPA Br. 24. According to EPA and intervenors,

“[t]he listings in the 2015 Rule are thus one, integral action

that” must “necessarily stand or fall as a whole because there

are no components to the regulatory text that can be treated

19

independently and severed.” Id. (internal quotation marks

omitted). Therefore, they argue, even if the Mexichem court

intended to invalidate the 2015 Rule’s HFC listings only in

part, the decision necessarily had the effect of invalidating

those listings in their entirety because there is no discrete,

severable text in the listings that could be struck to implement

the court’s intended partial vacatur.

EPA errs in focusing on the question whether the HFC

listings contained discrete, severable text that Mexichem could

have struck to implement a partial vacatur. It is a routine

feature of severability doctrine that a court may invalidate only

some applications even of indivisible text, so long as the “valid

applications can be separated from invalid ones.” Fallon et al.,

Hart & Wechsler’s: The Federal Courts and the Federal System

170 (7th ed. 2015). As the Supreme Court has explained, when

a court encounters statutory or regulatory text that is “invalid

as applied to one state of facts and yet valid as applied to

another,” it should “try to limit the solution to the problem” by,

for instance, enjoining the problematic applications “while

leaving other applications in force.” Ayotte v. Planned

Parenthood of N. New England, 546 U.S. 320, 328–29 (2006)

(citation omitted) (statute); see Greater New Orleans Broad.

Ass’n v. United States, 527 U.S. 173, 195–96 (1999)

(regulation). Otherwise, a court would be compelled to grant

facial relief in any successful as-applied challenge to a

statutory or regulatory provision. That of course is not the law.

Here, the Mexichem court followed the Supreme Court’s

guidance to “limit the solution to the problem” by vacating the

2015 Rule’s HFC listings only as applied to entities that EPA

lacks authority to regulate (those who had already switched

from ozone-depleting substances to HFCs), leaving the listings

intact as applied to other entities (those who had not). And in

vacating only certain applications of the 2015 Rule without

20

regard to whether the regulatory text is divisible in a

corresponding way, the Mexichem court acted in accordance

with our precedents.

Consider, in that regard, our decision in National Corn

Growers Ass’n v. EPA, 613 F.3d 266 (D.C. Cir. 2010). There,

we considered an EPA regulation that revoked all “tolerances”

(i.e., permissible residues in food) of the pesticide carbofuran,

thereby effectively banning use of carbofuran in food for

human consumption. Id. at 270. We vacated EPA’s rule as

applied to imported foods but left the rule in place as applied

to food produced domestically. See id. at 275. And we did so

without pausing to examine whether the regulatory text was

divisible in a manner corresponding to our partial vacatur. The

pertinent text in fact was not divisible in that way: it revoked

“all of the existing tolerances for residues of carbofuran,”

making no reference to—and drawing no distinction

between—import and domestic tolerances. Carbofuran; Final

Tolerance Revocations, 74 Fed. Reg. 23,046–23,052 (May 15,

2009). We nonetheless “vacate[d] EPA’s final rule” only “to

the extent it revoked the import tolerances for carbofuran,” 613

F.3d at 275, and we rejected challenges to the rule’s application

to domestic tolerances, id. at 272–74.

In Mexichem, we similarly did not engage in any express

severability analysis about the text of the 2015 Rule. Rather,

the decision makes clear its intention to separate unlawful

applications of the 2015 HFC listings from lawful ones, and to

vacate the 2015 Rule only as to the former. If EPA disagreed

with Mexichem’s invalidation only of certain applications

because the agency believed the 2015 Rule’s HFC listings

should be treated as an inseverable whole, see Carlson v. Postal

Regulatory Comm’n, 938 F.3d 337, 351 (D.C. Cir. 2019);

MD/DC/DE Broad. Ass’n v. FCC, 236 F.3d 13, 23 (D.C. Cir.

2001), the agency could have sought a full (rather than partial)

21

vacatur of the rule in a petition for rehearing. Indeed, our court

routinely entertains rehearing petitions about the appropriate

scope of relief. See, e.g., MD/DC/DE Broad. Ass’n v. FCC,

253 F.3d 732 (D.C. Cir. 2001); Davis Cty. Solid Waste Mgmt.

v. EPA, 108 F.3d 1454, 1455 (D.C. Cir. 1997) (per curiam);

Virginia v. EPA, 116 F.3d 499 (D.C. Cir. 1997) (per curiam).

But EPA did not do so.

The upshot is that, after Mexichem, the 2015 Rule’s HFC

listings remained applicable to the class of regulated entities

that continued to use ozone-depleting substances. The 2018

Rule, by suspending the HFC listings as applied to that group

of entities, changed those parties’ legal rights and obligations

from the status quo established by Mexichem. And because the

2018 Rule meets both prongs of the Bennett test for finality, we

have jurisdiction to consider the petitions for review before us

in this case.

III.

We now proceed to assess petitioners’ challenges to EPA’s

adoption of the Rule. Petitioners contend that the 2018 Rule

was a legislative rule and was thus improperly promulgated

without the required notice-and-comment procedures. They

further contend that the Rule is arbitrary and capricious. We

agree with the first of those arguments and therefore have no

occasion to consider the second one.

The Clean Air Act calls for EPA to employ notice-and-

comment procedures whenever it engages in the “promulgation

or revision of regulations under” Title VI. 42 U.S.C. § 7607(d);

see 5 U.S.C. § 553. That requirement, though, applies to the

promulgation only of legislative rules, not interpretive rules.

See Am. Mining Congress v. Mine Safety & Health Admin., 995

F.2d 1106, 1108–12 (D.C. Cir. 1993). Because the 2018 Rule

22

was not promulgated via notice and comment, the pivotal

question is whether the rule is legislative or interpretive.

The “line between interpretive and legislative rules” is

“fuzzy” and “enshrouded in considerable smog.” Id. at 1108

(citation omitted). Our decisions, however, set out a basic

taxonomy. A “legislative rule” is one that has “legal effect” or,

alternately, one that an agency promulgates with the “intent to

exercise” its “delegated legislative power” by speaking with

the force of law. Id. at 1109, 1112 (internal quotation marks

omitted). An “interpretive rule,” meanwhile, is one that

“derive[s] a proposition from an existing document,” such as a

statute, regulation, or judicial decision, “whose meaning

compels or logically justifies the proposition.” Catholic Health

Initiatives v. Sebelius, 617 F.3d 490, 494 (D.C. Cir. 2010)

(citation omitted). An interpretive rule, instead of creating

legal effects, thus puts the public on notice of pre-existing legal

obligations or rights. Here, the 2018 Rule has independent

legal effect beyond that compelled by Mexichem and reflects

EPA’s intent to exercise its delegated legislative power.

First, while EPA now describes the 2018 Rule as merely

interpretive, the Rule itself evinces the agency’s intent to speak

with the force of law. EPA concluded that “attempting to draw

the distinctions made by the court [in Mexichem] would present

practical difficulties,” that those distinctions were not reflected

in the text of the 2015 Rule, and that Mexichem’s partial

vacatur had generated “substantial confusion and uncertainty”

among regulated entities. 83 Fed. Reg. 18,433–35. EPA thus

relied “on its expertise . . . and its understanding of the 2015

Rule” to conclude that the 2015 HFC listings should be

suspended “in their entirety.” Id at 18,435. That manner of

action—identifying a practical problem ostensibly created by a

judicial decision and relying on agency expertise to put forward

a new and different resolution—is quintessentially legislative,

23

manifesting EPA’s intent to exercise its delegated legislative

power and speak with the force of law.

The 2018 Rule has the force of law because it suspends the

2015 Rule’s HFC listings for a class of regulated entities (those

continuing to use ozone-depleting substances) to whom the

2015 Rule still applied after Mexichem. Suspension of a rule

is “tantamount to amending or revoking a rule,” Clean Air

Council, 862 F.3d at 6, and “an agency action which has the

effect of suspending a duly promulgated regulation” (like the

2015 Rule) “is normally subject to APA rulemaking

requirements,” including notice-and-comment procedures.

Envtl. Def. Fund, Inc. v. Gorsuch, 713 F.2d 802 (D.C. Cir.

1983). Indeed, because the 2018 Rule had the effect of

amending what is undisputedly a legislative rule (the 2015

Rule), it too is a legislative rule subject to notice-and-comment

obligations: an “amendment to a legislative rule must itself be

legislative.” Sierra Club v. EPA, 873 F.3d 946, 952 (D.C. Cir.

2017).

Our dissenting colleague, while agreeing that the 2018

Rule constitutes final agency action, believes that the Rule is

interpretive rather than legislative, such that notice-and-

comment procedures should be inapplicable. But even

assuming an agency rule can determine “legal rights and

obligations” or carry “legal consequences” (so as to amount to

final agency action) but still lack “legal effects” (so as to fall

short of a legislative rule), see Cal. Cmtys. Against Toxics v.

EPA, 934 F.3d 627, 635 (D.C. Cir. 2019), the 2018 Rule is not

such a needle-threading rule. The 2018 Rule did not merely

interpret Mexichem’s partial vacatur of the 2015 Rule. The

2018 Rule instead expanded Mexichem’s partial vacatur into a

full vacatur, revoking those applications of the 2015 Rule’s bar

on use of HFCs that had remained standing after Mexichem.

24

Our colleague suggests that, insofar as Mexichem vacated

only certain applications of the 2015 Rule while leaving other

applications standing, our decision in that case disregarded the

regulatory history (specifically, a previous EPA rule referred to

as the “1994 Framework Rule”), and reached a resolution

inconsistent with severability principles. See Dissenting Op. 4,

11–15. As explained, however, Mexichem’s partial vacatur of

the 2015 Rule—its invalidation only of certain applications

without examining the severability of the regulatory text—

cohered with our precedents. See National Corn Growers, 613

F.3d 266; see also Illinois Commerce Comm’n v. ICC, 776 F.2d

355, 358–60 (D.C. Cir. 1985).

At any rate, the question for us is not whether Mexichem’s

partial vacatur of the 2015 Rule was correct at the time, or if

we should have examined the regulatory text’s severability in

that opinion. Mexichem’s partial vacatur, whether correct or

incorrect, is now final. And the question for us is whether EPA

in the 2018 Rule merely interpreted Mexichem’s partial vacatur

in the manner of an interpretive rule or instead altered the

decision’s legal effect in the manner of a legislative rule.

The agency did the latter, transforming Mexichem’s partial

vacatur into an across-the-board invalidation of the 2015

Rule’s HFC listings. The agency in fact affirmatively declined

“to draw the distinctions made by the court” in Mexichem. 83

Fed. Reg. 18,434. And the agency expressly “recognize[d] that

the court vacated the 2015 Rule [only] ‘to the extent that’ it

requires manufacturers to replace HFCs” and that the court had

otherwise “rejected the arbitrary and capricious challenges to

the HFC listing changes.” Id. at 18,435. But the agency

nonetheless opted to “implement the court’s vacatur by treating

it as striking the HFC listing changes in the 2015 Rule in their

entirety.” Id. (emphasis added). In other words, EPA “treated”

the decision as having a legal effect—full vacatur—that the

25

decision disclaimed. That is a legislative rule subject to notice-

and-comment procedures.

Intervenors submit that the agency’s failure to abide by

notice-and-comment requirements amounts to harmless error.

See Intervenors Br. 34–36. Of course, though, the entire

premise of notice-and-comment requirements is that an

agency’s decisionmaking may be affected by concerns aired by

interested parties through those procedures. For that reason,

we have “not been hospitable to government claims of

harmless error in cases in which the government . . . fail[ed] to

provide notice.” Allina Health Servs. v. Sebelius, 746 F.3d

1102, 1109 (D.C. Cir. 2014). And we have found cases “in

which a government agency seeks to promulgate a rule by

another name—evading altogether the notice and comment

requirements”—to be the “most egregious” breaches of notice-

and-comment obligations. Id.

This is such a case. EPA wholly failed to provide

petitioners (or any other interested parties) the opportunity to

comment on the best way to implement the distinctions drawn

by our court in Mexichem. Indeed, the very fact that EPA plans

to engage in full notice-and-comment rulemaking in the future

when developing a permanent replacement for the 2018 Rule

suggests that the agency, too, believes that comments from

interested parties may provide valuable input on the matter.

EPA’s failure to abide by notice-and-comment procedures

when promulgating the 2018 Rule then cannot be considered

harmless.

For substantially similar reasons, EPA’s error requires us

to vacate the 2018 Rule. In general, “vacatur is the normal

remedy” for a procedural violation, although we may remand

to the agency without vacatur based on “the seriousness of the

order’s deficiencies and the likely disruptive consequences of

26

vacatur.” Allina Health Servs., 746 F.3d at 1110 (internal

quotation marks omitted). Here, both considerations counsel

in favor of vacatur. First, “[f]ailure to provide the required

notice and to invite public comment—in contrast to the

agency’s failure . . . adequately to explain why it chose one

approach rather than another for one aspect of an otherwise

permissible rule—is a fundamental flaw that normally requires

vacatur of the rule.” Heartland Reg’l Med. Ctr. v. Sebelius,

566 F.3d 193, 199 (D.C. Cir. 2009) (internal quotation marks

omitted). And second, neither EPA nor intervenors have

identified any serious disruptive consequences of vacatur,

resting instead on the regulatory uncertainty that typically

attends vacatur of any rule. See EPA Br. 38–39.

None of this means that EPA was powerless to act in the

face of what it perceived to be practical difficulties and

regulatory uncertainty engendered by Mexichem’s partial

vacatur. First, as noted, EPA could have petitioned the

Mexichem court for rehearing, explaining that it believed the

HFC listings were inseverable and asking the court to vacate

the 2015 Rule in full. Second, EPA could have issued an

interpretive rule (without engaging in notice and comment) to

explain how it understood the Mexichem decision’s partial

vacatur to apply to certain gray areas identified in the 2018

Rule. See 5 U.S.C. § 553(b); 83 Fed. Reg. 18,434–35. Third,

EPA could have exercised its enforcement discretion to focus

its enforcement efforts on entities still subject to regulation

after Mexichem, or it could have resolved difficult questions

through case-by-case adjudications, cf. Blanca Tel. Co. v. FCC,

743 F.3d 860, 867 (D.C. Cir. 2014). Finally, EPA perhaps

could have attempted to invoke the good-cause exception to

promulgate an interim legislative rule without notice and

comment, pending its undertaking a full legislative rulemaking.

See 5 U.S.C. § 553(b).

27

We do not mean to prejudge the ultimate permissibility or

efficacy of any of those options. Rather, we mean only to

highlight that EPA had several options by which it could have

attempted to address the perceived difficulties associated with

implementing our decision in Mexichem. But the one option

EPA could not permissibly pursue was the one it chose:

promulgating a legislative rule without abiding by notice-and-

comment requirements and without invoking any exception to

those obligations.

* * * * *

For the foregoing reasons, we grant the petitions for

review, vacate the 2018 Rule, and remand to EPA for further

proceedings consistent with this opinion.

So ordered.

RAO, Circuit Judge, dissenting: In 2018, the

Environmental Protection Agency issued a guidance document

to provide clarity and regulatory certainty for stakeholders

affected by EPA’s 2015 Rule regulating hydrofluorocarbons

(“HFCs”) and our related decision in Mexichem Fluor, Inc. v.

EPA, 866 F.3d 451 (D.C. Cir. 2017). The majority classifies

the 2018 Guidance as a final legislative rule that should have

been promulgated through notice and comment procedures. I

agree that the 2018 Guidance is a final agency action subject to

our review. Unlike the majority, however, I would classify the

2018 Guidance as an interpretive rule that did not create new

rights or obligations and did no more than articulate the EPA’s

view of what was required by Mexichem in the “near term” and

pending further rulemaking. Because the 2018 Guidance was

an interpretive rule, notice and comment was not necessary. In

addition, EPA’s decision to treat Mexichem as vacating the

entire 2015 Rule was not arbitrary and capricious because it

was effectively compelled by Mexichem. In characterizing the

2018 Guidance as a legislative rule, the majority misinterprets

the EPA’s regulatory framework and unravels Mexichem’s

mandate. I respectfully dissent.

I.

The dispute in this case turns on the interplay between

Mexichem and the EPA’s implementation of that decision in

the 2018 Guidance. To understand the scope and consequences

of the 2018 Guidance requires analyzing “the idiosyncratic

regime of statutes and regulations that govern it.” Cal.

Communities Against Toxics v. EPA, 934 F.3d 627, 632 (D.C.

Cir. 2019). I begin with the original regulatory framework EPA

promulgated in 1994, because this provides essential context

for understanding the 2015 Rule, Mexichem, and the 2018

Guidance.

As the majority explains, the United States ratified the

Montreal Protocol in 1987 to help address the deterioration of

2

the ozone layer. After ratification, Congress amended the Clean

Air Act in 1990 by adding Title VI. See 42 U.S.C. § 7671 et

seq. The amendments require manufacturers and end-users to

phase out various substances that deplete the ozone layer. See

Mexichem, 866 F.3d at 454. For our purposes, the most relevant

provision is Section 612(c), which authorizes EPA to regulate

which chemicals can be used “to replace” ozone-depleting

substances. 42 U.S.C. § 7671k(c). 1

In 1994, the EPA promulgated a framework explaining

how the EPA will regulate HFCs and other substitutes for

ozone-depleting substances. See Protection of Stratospheric

Ozone, 59 Fed. Reg. 13,044 (Mar. 18, 1994) (“1994

Framework Rule”). As relevant here, the Framework Rule

specified that when a chemical is listed as an unacceptable

substitute, no person can continue to use it, even if that person

has already stopped using ozone-depleting substances. Id. at

13,148 (“No person may use a substitute after the effective date

of any rulemaking adding such substitute to the list of

unacceptable substitutes.”). For more than 20 years, EPA

interpreted “replace” under Section 612(c) to apply on an

ongoing basis, each time a person uses the substitute. Id. at

13,048. Under this interpretation, if EPA reclassifies an

acceptable substitute as unacceptable, no one may use it, even

persons who had previously stopped using ozone-depleting

substances. Id. (“[O]nce EPA identifies an unacceptable

substitute, any future use of such substitute is prohibited. Under

any other interpretation, EPA could never effectively prohibit

the use of any substitute, as some user could always start to use

1

The full text reads: “[T]he Administrator shall promulgate rules

under this section providing that it shall be unlawful to replace any

class I or class II substance with any substitute substance which the

Administrator determines may present adverse effects to human

health or the environment, where the Administrator has identified an

alternative.” 42 U.S.C. § 7671k(c).

3

it prior to EPA’s completion of the rulemaking required to list

it as unacceptable.”).

The EPA initially listed HFCs as acceptable substitutes for

ozone-depleting substances. See, e.g., Protection of

Stratospheric Ozone: Listing of Substitutes for Ozone-

Depleting Substances, 68 Fed. Reg. 4,004, 4,005–06 (Jan. 27,

2003). In 2015, the agency changed course and listed HFCs as

unacceptable because they have a significant effect on global

warming. See Protection of Stratospheric Ozone: Change of

Listing Status for Certain Substitutes Under the Significant

New Alternatives Policy Program, 80 Fed. Reg. 42,870 (July

20, 2015) (“2015 Rule”). The 2015 Rule applied to everyone,

including people who had already stopped using ozone-

depleting substances and had “replaced” them with HFCs. As

EPA emphasized, this consequence followed directly from the

1994 Framework Rule. Id. at 42,936–37.

In Mexichem, we rejected EPA’s longstanding

interpretation that the term “replace” encompasses the

continued use of a substitute by people who have already

stopped using ozone-depleting substances. We explained that

EPA’s “reading stretche[d] the word ‘replace’ beyond its

ordinary meaning.” Mexichem, 866 F.3d at 458. We held that

the EPA has no authority under Section 612(c) to prohibit the

use of HFCs by people who adopted them as a substitute for

ozone-depleting substances before the 2015 Rule went into

effect. See 866 F.3d at 456–61. As we explained, a party

“replaces” an ozone-depleting substance when it transitions to

an acceptable substitute; once it does that, the replacement is

over. Because people who have already made the switch to

HFCs are no longer using ozone-depleting substances, the EPA

cannot require them to stop using HFCs—at least not under

Section 612(c), which regulates only the initial replacement of

ozone-depleting substances. Indeed, we emphasized that the

4

EPA’s “boundless interpretation” “border[ed] on the absurd”

because it would give the agency “indefinite authority.” Id. at

459. While we rejected EPA’s interpretation of “replace,” we

held that EPA’s decision to list HFCs as unacceptable

substitutes was, as a general matter, not arbitrary and

capricious. See id. at 462–64. As a remedy, we “vacate[d] the

2015 Rule to the extent it require[d] manufacturers to replace

HFCs with a substitute substance.” Id. at 464.

After Mexichem, the 1994 Framework Rule remains in

effect, although its reasoning was substantially undermined by

our opinion. The majority overlooks this fact—perhaps

because Mexichem never discusses the 1994 Rule and suggests

in passing that the EPA’s interpretation of “replace” was “new”

to the 2015 Rule. See 866 F.3d at 458. The 2015 Rule, however,

did not articulate a “new” interpretation. Rather, before

Mexichem, the EPA consistently maintained that it could

prohibit the use of substitutes like HFCs regardless of whether

a person had already made the substitution before the

regulation went into effect.

In the wake of Mexichem, regulated entities were unsure

of the practical consequences of our remedy and

“experience[ed] substantial confusion and uncertainty

regarding the meaning of the vacatur in a variety of specific

situations.” See Protection of Stratospheric Ozone: Notification

of Guidance and a Stakeholder Meeting Concerning the

Significant New Alternatives Policy (SNAP) Program, 83 Fed.

Reg. 18,431, 18,434 (Apr. 27, 2018) (“2018 Guidance”). In the

2018 Guidance, the EPA sought to clarify how it would

implement Mexichem. In doing so, EPA reiterated that the 1994

Framework Rule—not the 2015 Rule—required that “[n]o

person may use a substitute after the effective date of any

rulemaking adding such substitute to the list of unacceptable

substitutes.” See id. at 18,433 (quoting 40 C.F.R. § 82.174 (the

5

1994 Framework Rule)). The 2018 Guidance emphasized that

prior to Mexichem, the 2015 Rule had operated exactly “like all

other actions EPA has taken implementing the 1994

Framework Rule over the last quarter-century”—namely to

require everyone to stop using the unacceptable substance,

irrespective of whether they had switched to the substitute prior

to the listing. Id. In other words, the agency maintained that the

interpretation invalidated by Mexichem originated in the 1994

Framework Rule.

In the 2018 Guidance, EPA recognized that Mexichem

vacated “the 2015 Rule ‘to the extent that’ it requires

manufacturers to replace HFCs.” Id. at 18,435. EPA proceeded

to analyze how to implement this directive with respect to the

2015 Rule, which “is comprised solely of tables listing …

certain substitutes for specific end-uses.” Id. at 18,434. While

Mexichem suggests that the 2015 Rule could apply to people

still using ozone-depleting substances, the tables in the Rule do

not “draw a distinction between persons using HFCs and those

using an [ozone-depleting substance].” Id. The agency

concluded that the “regulations as currently written do not

provide the distinctions that would be necessary to

accommodate the letter of the court’s vacatur.” Id. After all,

under the 1994 Framework Rule, every listing necessarily

applies to current and future users of a given substance. See id.

at 18,435 (“[T]the listing of HFC’s as unacceptable, or

acceptable subject to use restrictions, is the means by which the

2015 Rule ‘require[d] manufacturers to replace HFCs with a

substitute substance.’”). EPA explained that “[t]he narrower

language used by the court does not exist in either the 2015

Rule or the 1994 Framework Rule; nor do the distinctions

discussed above emerge when those two rules are read

together.” Id. at 18,434. Indeed, the EPA emphasized that to

implement a partial vacatur would require it “to drastically

rewrite the 2015 Rule,” which “would not be appropriate to

6

undertake … without undergoing notice and comment

rulemaking.” Id. at 18,435.

Pending additional notice and comment rulemaking, EPA

determined that the only way to implement Mexichem and to

provide guidance to regulated entities was to read our opinion

as vacating the HFC listing in its entirety. See id. EPA thus

interpreted and implemented Mexichem’s vacatur in the only

way it believed permissible given the indivisible listings in the

2015 Rule and the interpretation set forth in the 1994

Framework Rule. With this more complete regulatory context,

I turn to the appeal before us.

II.

We face two interrelated, yet distinct, inquiries in this case.

First, we must decide whether the EPA’s action was final, a

question about the availability of judicial review. See 5 U.S.C.

§ 704. Second, if the action was final, we must determine

whether it is a legislative or interpretive rule, a question about

the procedures the agency must follow. As our court has

recently observed, “although all legislative rules are final, not

all final rules are legislative, and the finality analysis is

therefore distinct from the test for whether an agency action is

a legislative rule.” Cal. Communities Against Toxics, 934 F.3d

at 631; cf. Nat’l Mining Ass’n v. McCarthy, 758 F.3d 243, 251

(D.C. Cir. 2014) (“[E]ven interpretive rules may be subject to

pre-enforcement judicial review.”). 2

2

As the majority frames these questions, the standards for finality

and legislative rules are essentially the same. Indeed, the majority

leaves open the possibility that the category of final, interpretive

rules may be a conceptual null set. Maj. Op. 23. This has no support

in the APA and is foreclosed by Supreme Court precedent. See U.S.

7

The majority conflates aspects of these two standards. For

the purposes of this case’s finality inquiry, we need ask only

whether the agency’s interpretation of Mexichem had “direct

and appreciable legal consequences.” Bennett v. Spear, 520

U.S. 154, 178 (1997). While I agree with the majority that the

EPA’s action is final under this standard, it does not matter

whether the 2018 Guidance created new legal obligations. A

final agency action can include interpretive rules that merely

state the agency’s interpretation of a statute, regulation, or

judicial decision.

The question of whether the 2018 Guidance created new

legal obligations is, however, relevant to the second inquiry—

whether this is legislative rule. Here I part ways with the

majority. Because the 2018 Guidance merely interpreted the

necessary consequences of our vacatur in Mexichem, the

Guidance is a final, interpretive rule that was reasonable and

not arbitrary and capricious.

A.

We have jurisdiction under the Clean Air Act to review the

2018 Guidance only if it was a “final action.” See 42 U.S.C.

§ 7607(b)(1). The term “final action” “is synonymous with the

term ‘final agency action’ as used in Section 704 of the”

Administrative Procedure Act (“APA”). Sierra Club v. EPA,

873 F.3d 946, 951 (D.C. Cir. 2017). To determine whether an

agency action is final, we apply the two-prong test set forth in

Bennett v. Spear: the action must both “mark the

consummation of the agency’s decisionmaking process,” and it

“must be one by which rights or obligations have been

determined, or from which legal consequences will flow.” 520

U.S. 154, 178 (1997) (quotation marks omitted). The parties

Army Corps of Eng’rs v. Hawkes Co., 136 S. Ct. 1807, 1815 (2016)

(observing that the Court frequently reviews interpretive rules).

8

and the majority all agree that the 2018 Guidance reflects the

consummation of the agency’s decisionmaking process, Maj.

Op. 12, so I focus on the second prong.

The central dispute is whether an agency action can have

a sufficiently concrete legal effect for the purposes of Bennett’s

second prong if it simply interprets a legal obligation that stems

from a different legal source. The majority focuses on whether

it was “Mexichem, not the 2018 Rule, that suspended the 2015

Rule’s HFC listings.” Maj. Op. 16. In the finality context,

however, it is unnecessary to determine whether Mexichem

directs suspension of the 2015 Rule or whether the 2018

Guidance independently creates that result. Under Bennett, a

final action is “one by which rights or obligations have been

determined, or from which legal consequences will flow.” 520

U.S. at 178 (quotation marks omitted). The legal consequences

do not necessarily have to flow from the rule itself. If they did,

an interpretive rule could never be final and reviewable, and

we have explicitly held that “even interpretive rules may be

subject to pre-enforcement judicial review.” Nat’l Mining

Ass’n, 758 F.3d at 251; see also U.S. Army Corps of Eng’rs v.

Hawkes Co., 136 S. Ct. 1807, 1815 (2016) (observing that the

Court frequently reviews agency decisions that simply “give

notice of how the [agency] interpret[s] the relevant statute”

(quotation marks omitted)) (discussing Frozen Food Express v.

United States, 351 U.S. 40, 41–44 (1956)). 3

3

The Supreme Court made clear in Hawkes that interpretive rules

can be final actions subject to review, which supersedes any

suggestion in Association of Flight Attendants-CWA, AFL-CIO v.

Huerta, that interpretive rules are not reviewable. See 785 F.3d 710,

713 (D.C. Cir. 2015) (“The guidance offered in Notice N8900.240

reflects nothing more than a statement of agency policy or an

interpretive rule. The Notice is therefore unreviewable.”).

9

An interpretive rule by definition does not create new

obligations, but instead interprets existing legal obligations

under statutes, regulations, and judicial decisions. To be final,

a rule simply has to determine which rights a party has under

the law, and a rule determines rights or obligations if its impact

is “sufficiently direct and immediate” and if it will have a

“direct effect” on “day-to-day” affairs. Abbott Labs. v.

Gardner, 387 U.S. 136, 152 (1967). Put slightly differently,

“[t]he core question is … whether the result of th[e] process is

one that will directly affect the” regulated parties. Franklin v.

Mass., 505 U.S. 788, 797 (1992); accord Dalton v. Specter, 511

U.S. 462, 470 (1994).

The 2018 Guidance was an action “by which rights or

obligations have been determined.” Bennett, 520 U.S. at 178

(quotation marks omitted). In Mexichem’s aftermath, there was

considerable confusion across several industries as to the

meaning of the court’s remedy. See 83 Fed. Reg. at 18,434. The

2018 Guidance explained how the EPA would implement

Mexichem. The agency’s interpretation directly affected

regulated parties: “EPA will not apply the HFC use restrictions

or unacceptability listings in the 2015 Rule for any purpose.”

Id. at 18,433. Thus, irrespective of whether the obligations

followed from our Mexichem decision or an independent

decision by EPA, the 2018 Guidance had an immediate and

practical impact and thus was a final agency action subject to

our review.

B.

The finality of the 2018 Guidance, however, does not

answer the question of whether it is a legislative or interpretive

rule. This question turns on whether the 2018 Guidance merely

articulated the agency’s understanding of Mexichem’s legal

implications, or whether the agency went further than

10

Mexichem and thus created new legal obligations. If the 2018

Guidance was an interpretive rule, the EPA’s decision to skip

notice and comment was perfectly acceptable. See Shalala v.

Guernsey Mem’l Hosp., 514 U.S. 87, 99 (1995) (“Interpretive

rules do not require notice and comment.”); see also 5 U.S.C.

§ 553(b)(3)(A) (“Except when notice or hearing is required by

statute, this subsection [about notice and comment] does not

apply—(A) to interpretative rules.”). On the other hand, if the

2018 Guidance was a legislative rule that brought about a

substantive change to the agency’s Title VI regulations, then

the procedures used were inadequate. See 42 U.S.C.

§ 7607(d)(1)(I) (requiring notice and comment rulemaking for

regulations promulgated under Title VI).

To determine whether a rule is legislative, we ask whether

the agency is exercising its statutory rulemaking authority to

promulgate rules that have the force of law and “impose legally

binding obligations or prohibitions.” Nat’l Mining Ass’n, 758

F.3d at 251; see also Am. Mining Cong. v. Mine Safety &

Health Admin., 995 F.2d 1106, 1109 (D.C. Cir. 1993).

Interpretive rules, on the other hand, “derive a proposition from

an existing document whose meaning compels or logically

justifies the proposition.” Catholic Health Initiatives v.

Sebelius, 617 F.3d 490, 494 (D.C. Cir. 2010). “[T]he critical

feature of interpretive rules is that they are issued by an agency

to advise the public of the agency’s construction of the statutes

and rules which it administers.” Perez v. Mortg. Bankers Ass’n,

135 S. Ct. 1199, 1204 (2015) (quotation marks omitted). Thus,

legislative rules impose new legally binding requirements,

whereas interpretive rules set forth the agency’s explanation of

existing legal requirements. Evaluating EPA’s action in light

of the Mexichem remedy as well as the existing regulatory

scheme demonstrates that the 2018 Guidance was an

interpretive rule.

11

As the majority recognizes, “EPA could have issued an

interpretive rule (without engaging in notice and comment) to

explain how it understood the Mexichem decision’s partial

vacatur to apply to certain gray areas identified.” Maj. Op. 26.

That is precisely what EPA did in the 2018 Guidance when it

stated why Mexichem compelled a prohibition on the use of

HFCs, absent further rulemaking. Mexichem held that EPA

could not interpret Section 612(c) to require people who had

already “replaced” ozone-depleting substances with HFCs to

make another replacement. Mexichem, 866 F.3d at 459

(“EPA’s strained reading of the term ‘replace’ contravenes the

statute and thus fails at Chevron step 1.”). In addition, our court

held that EPA had reasonably chosen to list HFCs as

unacceptable substitutes going forward. Id. at 462–64. The

resulting public confusion and uncertainty stemmed in part

from the fact that our court vacated the 2015 Rule “to the extent

that” it applied to people who had already switched to HFCs

from ozone-depleting substances. Our court remanded to the

EPA for further proceedings without conducting a severability

analysis or otherwise explaining how to implement the vacatur.

Thus, after Mexichem, a practical question remained about

how to implement the decision. Recognizing that “the agency

cannot remain silent on the implications of the court’s vacatur

until such time as the agency can complete a notice-and-

comment rulemaking,” the EPA provided a “near term”

interpretation of our decision. 83 Fed Reg. at 18,435. EPA

concluded that in light of the 2015 and 1994 Rules, the 2015

HFC listings could not be applied “for any purpose prior to

completion of rulemaking.” Id. Although our remedy in

Mexichem could arguably be read to suggest some type of

partial vacatur, the EPA concluded that “[t]he narrower

language used by the court does not exist in [ ] the 2015 Rule.”

Id. at 18,434. According to the EPA, because the Rule is

composed of nothing more than tables—tables that did not

12

make the distinction drawn by our court—the Rule could not

be vacated only in part. “[T]he listing of HFC’s as

unacceptable, or acceptable subject to use restrictions, is the

means by which the 2015 Rule ‘require[d] manufacturers to

replace HFCs with a substitute substance.’” See id. at 18,435

(quoting Mexichem, 866 F.3d at 462). Listing HFCs as

unacceptable necessarily had the effect our court said went

beyond EPA’s statutory authority, so there was nothing that

could be severed from the listing to separate those who had

already switched to HFCs from those who may switch in the

future. “Vacating the 2015 Rule ‘to the extent’ that it imposed

that requirement means vacating the listings. To apply the

court’s holding otherwise would be to drastically rewrite the

2015 Rule.” Id.

The EPA recognized that it could eventually create

sublistings for different types of HFC users, but “such additions

to the 2015 Rule would require notice-and-comment

rulemaking.” Id. at 18,434. Additional rulemaking would be

required not only to address the 2015 Rule’s indivisible

listings, but also to revisit EPA’s interpretation of “replace” in

the 1994 Framework Rule, which was never addressed by

Mexichem and therefore remained on the books, even if its

reasoning was substantially undermined. Id. Thus, pending

further rulemaking, EPA interpreted Mexichem as vacating the

entire list of HFCs. The majority says that the 2018 Guidance

is a legislative rule because the EPA “identif[ied] a practical

problem” and “rel[ied] on agency expertise to put forward a

new resolution.” Maj. Op. 22–23. Yet EPA never suggested it

was crafting a practical solution to a new problem. Rather, EPA

concluded this was the only course of action that was legally

permissible in light of the vacatur in Mexichem.

The majority today provides a different interpretation of

Mexichem, one that rewrites our decision and ignores the

13

regulatory framework still in place after Mexichem. To the

extent the majority seeks to provide a severability analysis not

provided by Mexichem, the majority’s conclusion is

inconsistent with our regulatory severability precedents and

also with the clear vacatur set forth in Mexichem. When

determining whether a regulation may be severed, the court

considers a two-part test. “First, the court must find that ‘the

agency would have adopted the same disposition regarding the

unchallenged portion [of the regulation] if the challenged

portion were subtracted.’” Carlson v. Postal Regulatory

Comm’n, 938 F.3d 337, 351 (D.C. Cir. 2019) (quoting Sierra

Club v. FERC, 867 F.3d 1357, 1366 (D.C. Cir. 2017)).

“Second, the parts of the regulation that remain must be able to

‘function sensibly without the stricken provision.’” Id. (quoting

Sorenson Commc’ns. Inc. v. FCC, 755 F.3d 702, 710 (D.C. Cir.

2014)). The “entire rule must be vacated” if severing only the

unlawful aspects “would severely distort the [agency’s]

program and produce a rule strikingly different from any the

[agency] has ever considered or promulgated in the lengthy

course of these proceedings.” MD/DC/DE Broads. Ass’n v.

FCC, 236 F.3d 13, 23 (D.C. Cir. 2001). Moreover, an agency

action should be vacated in its entirety if “[t]he intertwined

character of the … component parts gives rise to a substantial

doubt that a partial affirmance would comport with the

[agency’s] intent.” Tel. & Data Sys. Inc. v. FCC, 19 F.3d 42,

50 (D.C. Cir. 1994).

Here, the lawful and unlawful “parts” of the 2015 Rule

were not just “intertwined.” Id. They stemmed from the exact

same listing—indeed, the exact same words. The 2015 Rule’s

lawful applications could not survive independently when

Mexichem interpreted the statute in a manner fundamentally at

odds with the underlying 1994 Framework Rule. EPA noted in

the 2018 Guidance that it plans to consider to what extent the

1994 Framework Rule must be modified through future notice

14

and comment rulemaking. Until that occurs, however, the

majority’s solution produces a rule inconsistent with the

agency’s existing regulatory framework for classifying

replacements for ozone-depleting substances.

If the agency had chosen to adopt the majority’s

interpretation after Mexichem, the EPA would have been

required to engage in notice and comment rulemaking. In the

2018 Guidance, EPA noted numerous difficult questions raised

by our decision in Mexichem that the agency planned to

address. See, e.g., 83 Fed. Reg. at 18,435–36 (listing the

questions the agency plans on considering in the future,

including “whether EPA should revisit specific provisions of

the 1994 Framework Rule … to establish distinctions between

users still using [ozone-depleting substances] and those who

have already replaced” them; “[w]hether EPA should

distinguish between product manufacturers and other users”;

and “[w]hether EPA should clarify when the replacement of an

[ozone-depleting substance] occurs: e.g., on a facility-by-

facility basis, or on a product-by-product basis”). As the EPA

reiterated in the 2018 Guidance, the 2015 Rule functioned the

same way as every other listing since 1994: The listing of a

substance as unacceptable would apply to everyone

manufacturing or using that substance. Because the majority

overlooks the existing regulatory framework, it fails to

appreciate that notice and comment rulemaking would be

required to implement its interpretation of Mexichem.

Under the majority’s holding, the 2015 Rule will now

function differently from every other rule promulgated by EPA

under Section 612(c). Instead of following our precedents in

the context of regulatory severability, 4 the majority interprets

4

Many of the cases relied on by the majority do not involve

severability at all. See, e.g., Ayotte v. Planned Parenthood of

Northern New England, 546 U.S. 320 (2006); Greater New Orleans

15

what it considers to be our court’s “intention” in Mexichem.

Even though Mexichem did not engage in any express

severability analysis, the majority concludes that “the decision

makes clear its intention to separate unlawful applications of

the 2015 HFC listings from lawful ones, and to vacate the 2015

Rule only as to the former.” Maj. Op. 20; see also id. at 18

(“[O]ur decision in Mexichem reinforced throughout an

intention only to forbid EPA from applying the 2015 Rule’s

HFC listings to a discrete set of regulated parties.”). Yet

Mexichem did not enjoin particular applications of the 2015

Rule. Nor did it hold the regulation unlawful as applied to

specific parties. Nor did it remand without vacatur for the EPA

to determine how to apply our holding.

Instead, our court repeatedly stated that it was vacating the

2015 Rule insofar as it applies to people who have already

switched to HFCs. See Mexichem, 866 F.3d at 462. To vacate

is to do more than enjoin or modify; it is to invalidate. Not only

did we vacate the Rule, we said that by promulgating it, the

EPA exceeded its statutory authority to a degree that

“border[ed] on the absurd.” Id. at 459.

As EPA explained, “The court clearly intended to vacate

the 2015 Rule to some ‘extent.’” 83 Fed Reg. at 18,434. A

different remedy—for instance, one enjoining particular

Broad. Ass’n v. United States, 527 U.S. 173 (1999). Relatedly, the

majority claims National Corn Growers v. EPA is relevant because

the court vacated a rule “to the extent” it applied to imports, even

though the rule in question did not draw a distinction between

imports and other goods. Maj. Op. 20. (citing 613 F.3d 266, 275

(D.C. Cir. 2010)). That case also failed to address severability. While

National Corn Growers, like Mexichem, vacated a rule “to the

extent” it had unlawful applications, the case said nothing about the

interpretive question that necessarily followed—namely, what it

means to vacate a rule to that extent.

16

applications—would have been inconsistent with the question

presented in Mexichem, which was “whether Section 612 of the

Clean Air Act authorizes the 2015 Rule.” Id. at 456. The

question presented did not concern the application of the 2015

Rule to particular persons, but instead raised a challenge to the

2015 Rule as a whole.

Nothing in Mexichem suggested that EPA could use

enforcement discretion to implement our holding that EPA’s

interpretation exceeded the authority in Section 612(c). 5 Today

the majority chooses to “sever” the 2015 Rule, not by vacating

as Mexichem directed, but by rewriting the Rule to apply to a

subset of regulated entities. Under the majority’s interpretation,

not a single word of the 2015 Rule is vacated; instead, the Rule

will apply as written in some cases but not others. See Maj. Op.

21 (“[A]fter Mexichem, the 2015 Rule’s HFC listings remained

applicable to the class of regulated entities that continued to use

ozone-depleting substances.”). As a formal matter, the text of

the 2015 Rule remains exactly the same. Yet as a practical

matter, it must be read with a judicial asterisk, directing the

agency to execute the 2015 Rule in a manner at odds with both

5

The majority suggests enforcement discretion as an alternative for

implementing Mexichem. Maj. Op. 26. To permit an agency to

implement a partial vacatur through enforcement discretion—thus

leaving the offending rule on the books—undermines this court’s

authority and produces further uncertainty. We should encourage

agencies to distinguish between regulated parties through clear

interpretive guidance, rather than through ad hoc discretion. For

similar reasons, EPA should be wary of the majority’s suggestion to

attempt using the good-cause exception for interim legislative rules,

Maj. Op. 26, another limited regulatory practice this court has

cautioned against abusing. See Mack Trucks, Inc. v. EPA, 682 F.3d

87, 93 (D.C. Cir. 2012) (“We have repeatedly made clear that the

good cause exception is to be narrowly construed and only

reluctantly countenanced.” (quotation marks omitted)).

17

the plain meaning and EPA’s existing regulatory framework.

By contrast, the EPA’s 2018 Guidance is consistent with

Mexichem, the text and structure of the 2015 Rule, and other

regulations under Section 612(c). I would therefore hold that

the 2018 Guidance was an interpretive rule for which no notice

and comment was required.

C.

The petitioners also argue that the EPA’s decision to delist

HFCs was arbitrary and capricious. The majority does not

reach this issue because it concludes that the 2018 Guidance

was a legislative rule and therefore must be vacated because

the EPA did not follow notice and comment procedures.

Because I classify the 2018 Guidance as an interpretive rule, I

proceed to explain why petitioners’ arbitrary and capricious

challenge lacks merit.

The APA mandates that the federal courts “hold unlawful

and set aside agency action, findings and conclusions found to

be—(A) arbitrary, capricious, an abuse of discretion, or

otherwise not in accordance with the law.” 5 U.S.C.

§ 706(2)(A). We must ask whether the agency “examine[d] the

relevant data and articulate[d] a satisfactory explanation for its

action[,] … whether the decision was based on a consideration

of the relevant factors and whether there has been a clear error

of judgment.” Motor Vehicle Mfrs. Ass’n of U.S., Inc. v. State

Farm Mut. Auto. Ins. Co., 463 U.S. 29, 43 (1983); see also

Encino Motorcars, LLC v. Navarro, 136 S. Ct. 2117, 2125

(2016) (“One of the basic procedural requirements of

administrative rulemaking is that an agency must give adequate

reasons for its decisions.”).

The petitioners argue that the EPA’s analysis was arbitrary

and capricious because it did not “show that there are good

reasons for the new policy,” NRDC Br. at 36 (quoting Encino

18

Motorcars, LLC, 136 S. Ct. at 2126), and because it failed to

account for the contribution of additional HFCs to “climate

change or its attendant harms.” Id. at 40. An action is arbitrary

and capricious, however, only if the agency failed to consider

“the relevant data.” State Farm Mut. Auto. Ins., 463 U.S. at 43.

We look to “whether the decision was based on a consideration

of the relevant factors and whether there has been a clear error.”

Marsh v. Ore. Nat. Res. Council, 490 U.S. 360, 378 (1989).

The petitioners essentially argue the EPA should have

addressed policy considerations. Policy considerations,

however, were not relevant to interpreting Mexichem, and

therefore EPA was not required to consider them. See Black

Citizens for a Fair Media v. FCC, 719 F.2d 407, 431 n.15 (D.C.

Cir. 1983) (explaining that agencies can “ignore those factors

it considers irrelevant to the statutory scheme”); TransCanada

Pipelines Ltd. v. FERC, 878 F.2d 401, 413 (D.C. Cir. 1989)

(“FERC acknowledged this evidence and ignored it as

irrelevant. We agree that this evidence, by itself, fails to

contradict FERC’s [ ] theory.” (citation omitted)).

As discussed, the 2018 Guidance did nothing more than

interpret Mexichem, and EPA’s interpretation properly

implemented our court’s mandate. In interpreting our opinion,

it simply would not have been relevant to consider what

environmental impacts our decision may have had. The EPA

could not choose to disregard our mandate because it thought a

different outcome was better on policy grounds. An agency

does not act arbitrarily or capriciously when it takes an action

that is required by law. See US Magnesium, LLC v. EPA, 630

F.3d 188, 193 (D.C. Cir. 2011) (holding that an agency’s action

could not have been arbitrary or capricious because the agency

did not have discretion to adopt a different choice); Fitts v. Fed.

Nat. Mortg. Ass’n, 236 F.3d 1, 6 (D.C. Cir. 2001) (explaining

that the exercise of agency “discretion” is necessary to “justify

the application of arbitrary and capricious review”).

19

Ultimately, the petitioners’ argument that the EPA should

have given more reasons for its “new policy” is premised on

their view that the 2018 Guidance was a legislative rule that

created new obligations. Because it was instead an interpretive

rule, additional policy considerations were not relevant, so the

agency’s failure to consider them was not arbitrary and

capricious.

***

Notice and comment rulemaking is a central part of the

administrative framework set forth in the APA and the Clean

Air Act. When an agency issues a legislative rule by exercising

its delegated authority to establish new obligations with the

force of law, it must follow these procedures. In the 2018

Guidance, however, EPA simply interpreted the immediate and

necessary consequences of our decision in Mexichem and left

rewriting the regulatory framework for future notice and

comment rulemaking. Because the 2018 Guidance advised the

public of the EPA’s interpretation of legal obligations created

by this court, it was an interpretive rule properly issued without

notice and comment procedures. I respectfully dissent.