United States Court of Appeals

FOR THE DISTRICT OF COLUMBIA CIRCUIT

Argued February 17, 2017 Decided August 8, 2017

No. 15-1328

MEXICHEM FLUOR, INC.,

PETITIONER

v.

ENVIRONMENTAL PROTECTION AGENCY,

RESPONDENT

THE CHEMOURS COMPANY FC, LLC, ET AL.,

INTERVENORS

Consolidated with 15-1329

On Petitions for Review of Final Action by the 

United States Environmental Protection Agency

Dan Himmelfarb argued the cause for petitioners. With 

him on the joint briefs were John S. Hahn, Roger W. Patrick, 

Matthew A. Waring, William J. Hamel, W. Caffey Norman, T. 

Michael Guiffré, and Kristina V. Foehrkolb.

Dustin J. Maghamfar, Attorney, U.S. Department of 

Justice, argued the cause for respondent. On the brief were 

John C. Cruden, Assistant Attorney General, Elizabeth B. 

Dawson, Attorney, U.S. Department of Justice, and Jan 
2

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

Protection Agency.

Thomas A. Lorenzen argued the cause for intervenors The 

Chemours Company FC, LLC, and Honeywell International 

Inc. in support of respondent. With him on the brief were 

Robert J. Meyers, Sherrie A. Armstrong, Jonathan S. Martel, 

and Eric A. Rey.

David Doniger, Benjamin Longstreth, Melissa J. Lynch, 

and Emily K. Davis were on the brief for intervenor Natural 

Resources Defense Council in support of respondent.

Before: BROWN, KAVANAUGH, and WILKINS, Circuit 

Judges.

Opinion for the Court filed by Circuit Judge KAVANAUGH, 

with whom Circuit Judge BROWN joins, and with whom Circuit 

Judge WILKINS joins as to Part I and Part III. 

Opinion concurring in part and dissenting in part filed by 

Circuit Judge WILKINS.

KAVANAUGH, Circuit Judge: The separation of powers 

and statutory interpretation issue that arises again and again in 

this Court is whether an executive or independent agency has 

statutory authority from Congress to issue a particular 

regulation. In this case, we consider whether EPA had 

statutory authority to issue a 2015 Rule regulating the use of 

hydrofluorocarbons, known as HFCs. 

According to EPA, emissions of HFCs contribute to 

climate change. In 2015, EPA therefore issued a rule that 

restricted manufacturers from making certain products that 

contain HFCs. HFCs have long been used in a variety of 
3

familiar products – in particular, in aerosol spray cans, motor 

vehicle air conditioners, commercial refrigerators, and foams. 

But as a result of the 2015 Rule, some of the manufacturers that 

previously used HFCs in their products no longer may do so. 

Instead, those manufacturers must use other EPA-approved 

substances in their products. 

As statutory authority for the 2015 Rule, EPA has relied 

on Section 612 of the Clean Air Act. 42 U.S.C. § 7671k. 

Section 612 requires manufacturers to replace ozone-depleting 

substances with safe substitutes.

The fundamental problem for EPA is that HFCs are not 

ozone-depleting substances, as all parties agree. Because 

HFCs are not ozone-depleting substances, Section 612 would 

not seem to grant EPA authority to require replacement of 

HFCs. Indeed, before 2015, EPA itself maintained that Section 

612 did not grant authority to require replacement of nonozone-depleting substances such as HFCs. But in the 2015 

Rule, for the first time since Section 612 was enacted in 1990, 

EPA required manufacturers to replace non-ozone-depleting 

substances(HFCs) that had previously been deemed acceptable 

by the agency. In particular, EPA concluded that some HFCs

could no longer be used by manufacturers in certain products, 

even if the manufacturers had long since replaced ozonedepleting substances with HFCs. 

EPA’s novel reading of Section 612 is inconsistent with 

the statute as written. Section 612 does not require (or give 

EPA authority to require) manufacturers to replace non-ozonedepleting substances such as HFCs. We therefore vacate the 

2015 Rule to the extent it requires manufacturers to replace 

HFCs, and we remand to EPA for further proceedings 

consistent with this opinion.
4

I

A

In the 1980s, an international movement developed to

combat depletion of the ozone layer. Depletion of the ozone 

layer exposes people to more of the sun’s harmful ultraviolet 

light, thereby increasing the incidence of skin cancer, among 

other harms. The international efforts to address ozone 

depletion culminated in the Montreal Protocol, an international 

agreement signed in 1987 by the United States and 

subsequently ratified by every nation in the United Nations. 

The Protocol requires signatory nations to regulate the 

production and use of a variety of ozone-depleting substances. 

Montreal Protocol on Substances that Deplete the Ozone 

Layer, opened for signature Sept. 16, 1987, S. Treaty Doc. No. 

100-10, 1522 U.N.T.S. 29.

Congress implemented U.S. obligations under the 

Montreal Protocol by enacting, with President George H.W. 

Bush’s signature, the 1990 Amendments to the Clean Air Act. 

Those amendments added a new Title VI to the Clean Air Act. 

Title VI regulates ozone-depleting substances. 

Title VI identifies two classes of ozone-depleting 

substances: “class I” and “class II” substances. 42 U.S.C. 

§ 7671a(a), (b). Section 612(a), one of the key provisions of 

Title VI, requires manufacturers to replace those ozonedepleting substances: “To the maximum extent practicable,

class I and class II substances shall be replaced by chemicals, 

product substitutes, or alternative manufacturing processes that 

reduce overall risks to human health and the environment.” Id.

§ 7671k(a). With a few exceptions, Title VI requires 

manufacturers to phase out their use of some ozone-depleting 
5

substances by 2000, and to phase out their use of other ozonedepleting substances by 2015. Id. §§ 7671c(b)-(c), 7671d(a). 

When manufacturers stop using ozone-depleting

substances in their products, manufacturers may need to

replace those substances with a substitute substance. Under 

Section 612(a), EPA may require manufacturers to use safe

substitutes when the manufacturers replace ozone-depleting

substances. Id. § 7671k(a). 

To implement the Section 612(a) requirement that ozonedepleting substances be replaced with safe substitutes, Section 

612(c) requires EPA to publish a list of both safe and prohibited

substitutes:

Within 2 years after November 15, 1990, the 

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 to such replacement that –

(1) reduces the overall risk to human health and the 

environment; and 

(2) is currently or potentially available.

The Administrator shall publish a list of (A) the substitutes 

prohibited under this subsection for specific uses and 

(B) the safe alternatives identified under this subsection 

for specific uses. 

Id. § 7671k(c). In short, Section 612(c) requires EPA to issue 

a list of both authorized and prohibited substitute substances

based on the safety and availability of the substances. 
6

Importantly, the lists of safe substitutes and prohibited

substitutes are not set in stone. Section 612(d) provides: “Any 

person may petition the Administrator to add a substance to the 

lists under subsection (c) of this section or to remove a 

substance from either of such lists.” Id. § 7671k(d). In other 

words, if EPA places a substance on the list of safe substitutes, 

EPA may later change its classification and move the substance

to the list of prohibited substitutes (or vice versa).

In 1994, EPA promulgated regulations to implement 

Section 612(c). See Protection of Stratospheric Ozone, 59 Fed. 

Reg. 13,044 (Mar. 18, 1994). At the time, EPA indicated that 

once a manufacturer has replaced its ozone-depleting

substances with a non-ozone-depleting substitute, Section 

612(c) does not give EPA authority to require the manufacturer 

to later replace that substitute with a different substitute. EPA 

explained that Section 612(c) “does not authorize EPA to 

review substitutes for substances that are not themselves”

ozone-depleting substances covered under Title VI. EPA 

Response to Comments on 1994 Significant New Alternatives 

Policy Rule, J.A. 50. 

B

Hydrofluorocarbons, known as HFCs, are substances that 

contain hydrogen, fluorine, and carbon. When HFCs are 

emitted, they trap heat in the atmosphere. They are therefore

“greenhouse gases.” But HFCs do not deplete the ozone layer. 

As a result, HFCs are not ozone-depleting substances covered 

by Title VI of the Clean Air Act. Instead, HFCs are potential 

substitutes for ozone-depleting substances in certain products. 

In 1994, acting pursuant to its authority under Section 

612(c), EPA concluded that certain HFCs were safe substitutes 
7

for ozone-depleting substances when used in aerosols, motor 

vehicle air conditioners, commercial refrigerators, and foams, 

among other things. See Protection of Stratospheric Ozone, 59 

Fed. Reg. at 13,122-46. Over the next decade, EPA added

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

products. See, e.g., Protection of Stratospheric Ozone: Listing 

of Substitutes for Ozone-Depleting Substances, 68 Fed. Reg. 

4004, 4005 (Jan. 27, 2003); Protection of Stratospheric Ozone; 

Listing of Substitutes for Ozone-Depleting Substances, 64 Fed. 

Reg. 22,982, 22,984 (Apr. 28, 1999). 

As a result, in the 1990s and 2000s, many businesses 

stopped using ozone-depleting substances in their products. 

Many businesses replaced those ozone-depleting substances

with HFCs. HFCs became prevalent in many products. HFCs 

have served as propellants in aerosol spray cans, as refrigerants 

in air conditioners and refrigerators, and as blowing agents that 

create bubbles in foams. 

Over time, EPA learned more about the effects of

greenhouse gases such as HFCs. In 2009, EPA concluded that 

greenhouse gases may contribute to climate change, increasing

the incidence of mortality and the likelihood of extreme 

weather events such as floods and hurricanes. See 

Endangerment and Cause or Contribute Findings for 

Greenhouse Gases Under Section 202(a) of the Clean Air Act, 

74 Fed. Reg. 66,496, 66,497-98 (Dec. 15, 2009). 

In 2013, President Obama announced that EPA would seek 

to reduce emissions of HFCs because HFCs contribute to 

climate change. EXECUTIVE OFFICE OF THE PRESIDENT, THE 

PRESIDENT’S CLIMATE ACTION PLAN 10 (2013). The 

President’s Climate Action Plan indicated that “the 

Environmental Protection Agency will use its authority 
8

through the Significant New Alternatives Policy Program” of 

Section 612 to reduce HFC emissions. Id.

Consistent with the Climate Action Plan, EPA

promulgated a Final Rule in 2015 that moved certain HFCs 

from the list of safe substitutes to the list of prohibited 

substitutes. 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) [hereinafter Final Rule]. In doing so, EPA prohibited 

the use of certain HFCs in aerosols, motor vehicle air 

conditioners, commercial refrigerators, and foams – even if 

manufacturers of those products had long since replaced ozonedepleting substances with HFCs. Id. at 42,872-73. 

Therefore, under the 2015 Rule, manufacturers that used

those HFCs in their products are no longer allowed to do so.

Those manufacturers must replace the HFCs with other 

substances that are on the revised list of safe substitutes. 

In the 2015 Rule, EPA relied on Section 612 of the Clean 

Air Act as its source of statutory authority. EPA said that 

Section 612 allows EPA to “change the listing status of a 

particular substitute” based on “new information.” Id. at 

42,876. EPA indicated that it had new information about 

HFCs: Emerging research demonstrated that HFCs were

greenhouse gases that contribute to climate change. See id. at 

42,879. EPA therefore concluded that it had statutory authority 

to move HFCs from the list of safe substitutes to the list of 

prohibited substitutes. Because HFCs are now prohibited 

substitutes, EPA claimed that it could also require the 

replacement of HFCs under Section 612(c) of the Clean Air Act

even though HFCs are not ozone-depleting substances. 
9

Mexichem Fluor and Arkema are businesses that make

HFC-134a for use in a variety of products. The 2015 Rule 

prohibits the use of HFC-134a in certain products. The 

companies have petitioned for review of the 2015 Rule. They 

raise two main arguments. First, they argue that the 2015 Rule 

exceeds EPA’s statutory authority under Section 612 of the 

Clean Air Act. In particular, they contend that EPA does not 

have statutory authority to require manufacturers to replace 

HFCs, which are non-ozone-depleting substances, with 

alternative substances. Second, they allege that EPA’s decision 

in the 2015 Rule to remove HFCs from the list of safe 

substitutes was arbitrary and capricious because EPA failed to 

adequately explain its decision and failed to consider several 

important aspects of the problem. We address those arguments 

in turn.

II

A

We first consider whether Section 612 of the Clean Air Act

authorizes the 2015 Rule.

In 1987, the United States signed the Montreal Protocol. 

The Montreal Protocol is an international agreement that has 

been ratified by every nation that is a member of the United 

Nations. The Protocol requires nations to regulate the 

production and use of certain ozone-depleting substances. See 

Montreal Protocol on Substances that Deplete the Ozone 

Layer, opened for signature Sept. 16, 1987, S. Treaty Doc. No. 

100-10, 1522 U.N.T.S. 29.

In 1990, in part to implement U.S. obligations under the 

Protocol and to regulate the production and use of ozone-
10

depleting substances, Congress added a new Title to the Clean 

Air Act: Title VI. Among Title VI’s provisions is Section 612. 

Section 612(a) of the Act provides: “To the maximum 

extent practicable,” ozone-depleting substances that are 

covered under Title VI “shall be replaced by chemicals, 

product substitutes, or alternative manufacturing processes that 

reduce overall risks to human health and the environment.” 42 

U.S.C. § 7671k(a). Title VI sets phase-out dates for those 

ozone-depleting substances. Id. §§ 7671c, 7671d. 

To implement Section 612(a), EPA maintains lists of both 

safe substitutes and prohibited substitutes for ozone-depleting 

substances. The provision governing those lists, Section 

612(c), provides: It “shall be unlawful to replace any” ozonedepleting substance that is covered under Title VI “with any 

substitute substance” that is on EPA’s list of “prohibited”

substitutes. Id. § 7671k(c). A manufacturer that violates 

Section 612(c) can be subject to substantial civil and criminal 

penalties. See id. § 7413(b), (c).1 

In the years since 1990, many manufacturers of the 

products relevant here – aerosols, motor vehicle air 

conditioners, commercial refrigerators, and foams – have 

stopped using ozone-depleting substances in those products.

Manufacturers have often replaced those ozone-depleting 

substances with HFCs that have long been on the list of safe 

substitutes.

 

1 Although we focus primarily on product manufacturers in this 

case, our interpretation of Section 612(c) applies to any regulated 

parties that must replace ozone-depleting substances within the 

timelines specified by Title VI. See, e.g., 42 U.S.C. §§ 7671c, 7671d. 
11

In the 2015 Rule, acting under the authority of Section 

612(c), EPA moved some HFCs from the list of safe substitutes 

to the list of prohibited substitutes. As a result, manufacturers 

replacing ozone-depleting substances can no longer use those 

HFCs as a safe substitute. Even more importantly for present 

purposes, under the Rule, manufacturers that have already 

replaced ozone-depleting substances with HFCs can no longer 

use those HFCs in their products. 

In this case, all parties agree that EPA possesses statutory 

authority to require manufacturers to replace ozone-depleting 

substances within the timelines specified by Title VI –

generally by 2000 for some ozone-depleting substances, and by 

2015 for other ozone-depleting substances. See, e.g., 42 U.S.C. 

§§ 7671c, 7671d. If a substance on the safe substitutes list is 

later found to be an ozone-depleting substance, EPA possesses 

direct statutory authority to order the replacement of that 

ozone-depleting substance in accordance with those statutory 

timelines.

All parties in this case also agree that EPA may change the 

lists of safe and prohibited substitutes based on EPA’s 

assessment of the risks that those substitutes pose for “human 

health and the environment.” Id. § 7671k(c); see id.

§ 7671k(d). It follows that Section 612(c) allows EPA to move 

a substitute from the list of safe substitutes to the list of 

prohibited substitutes. Therefore, assuming that all other 

statutory criteria are satisfied, EPA may move HFCs from the 

list of safe substitutes to the list of prohibited substitutes, as it 

did in the 2015 Rule. 

In addition, all parties agree that, under Section 612(c), 

EPA may prohibit a manufacturer from replacing an ozonedepleting substance that is covered under Title VI with a 

prohibited substitute. It follows that EPA may bar any
12

manufacturers that still make products that contain ozonedepleting substances from replacing those ozone-depleting

substances with HFCs. Of course, that aspect of the 2015 Rule 

is not a big deal as of now because there are few (if any) 

manufacturers that still make products that use ozone-depleting 

substances.2

The key dispute in this case is whether EPA has authority 

under Section 612(c) to prohibit manufacturers from making 

products that contain HFCs if those manufacturers already 

replaced ozone-depleting substances with HFCs at a time when

HFCs were listed as safe substitutes. In those circumstances,

does EPA have authority to require a manufacturer to now 

replace HFCs, which are non-ozone-depleting substances, with 

another substitute?

For many years, EPA itself stated that it did not possess

authority under Section 612(c) to require the replacement of 

non-ozone-depleting substances. For example, in 1994, EPA 

explained that Section 612(c) “does not authorize EPA to 

review substitutes for substances that are not themselves” 

ozone-depleting substances. EPA Response to Comments on

1994 Significant New Alternatives Policy Rule, J.A. 50. Two 

years later, EPA reiterated that interpretation: EPA explained 

that it “does not regulate the legitimate substitution” of one 

substance for another “first generation non-ozone-depleting”

substance. EPA Response to OZ Technology’s Section 612(d) 

Petition, J.A. 145.

 

2 The parties disagree over whether, as a factual matter, any

manufacturers still make products that use ozone-depleting 

substances. EPA says yes. Mexichem and Arkema say no. We need 

not resolve that factual dispute here, as it has no bearing on our legal 

analysis of the meaning of Section 612(c). 
13

EPA now argues that it actually possesses such authority

under the statute. For the first time, EPA has sought to order 

the replacement of a non-ozone-depleting substitute that had 

previously been deemed acceptable by the agency.

3

 

EPA’s new interpretation of Section 612(c) depends on the 

word “replace.” As noted above, Section 612(c) makes it 

unlawful to “replace” an ozone-depleting substance that is 

covered under Title VI with a substitute substance that is on the 

list of prohibited substitutes. 42 U.S.C. § 7671k(c). EPA 

recognizes that manufacturers “replace” an ozone-depleting 

substance when the manufacturers initially replace that ozonedepleting substance with a safe substitute. But EPA argues that 

the initial substitution is not the only time when manufacturers 

“replace” an ozone-depleting substance. EPA claims that a 

manufacturer continues to “replace” the ozone-depleting 

substance every time the manufacturer uses the substitute

substance, indefinitely into the future. According to EPA, 

replacement is not a one-time occurrence but a never-ending 

process. In EPA’s view, because manufacturers continue to 

“replace” ozone-depleting substances with HFCs every time 

they use HFCs in their products, EPA continues to have

authority to require manufacturers to stop using HFCs and to 

use a different substitute.

EPA’s current reading stretches the word “replace” 

beyond its ordinary meaning. As relevant here, the word 

 

3 During oral argument, EPA conceded that it had never 

previously moved a non-ozone-depleting substance from the list of 

safe substitutes to the list of prohibited substitutes. Counsel for EPA 

stated: “I believe it is correct that the prior de-listings have involved 

ozone depleting substitutes, and I may not be correct for that, but we 

can assume for this morning that that is correct.” Tr. of Oral Arg. at 

14. Since the time of oral argument, EPA has not made any filings 

to this Court to retract that concession.
14

“replace” means to “take the place of.” THE AMERICAN 

HERITAGE DICTIONARY OF THE ENGLISH LANGUAGE (5th ed. 

2017 online); WEBSTER’S THIRD NEW INTERNATIONAL 

DICTIONARY 1925 (1993); THE OXFORD ENGLISH DICTIONARY

642 (2d ed. 1989). In common parlance, the word “replace” 

refers to a new thing taking the place of the old. For example, 

President Obama replaced President Bush at a specific moment 

in time: January 20, 2009, at 12 p.m. President Obama did not 

“replace” President Bush every time President Obama

thereafter walked into the Oval Office. By the same token, 

manufacturers “replace” an ozone-depleting substance when

they transition to making the same product with a substitute 

substance. After that transition has occurred, the replacement 

has been effectuated, and the manufacturer no longer makes a

product that uses an ozone-depleting substance. At that point, 

there is no ozone-depleting substance to “replace,” as EPA 

itself long recognized.4 

Under EPA’s current interpretation of the word “replace,” 

manufacturers would continue to “replace” an ozone-depleting

substance with a substitute even 100 years or more from now. 

EPA would thereby have indefinite authority to regulate a

 

4 The dissenting opinion says that the word “replace” may mean

“to provide a substitute for,” rather than “to take the place of.” 

Dissenting Op. at 4, 6. But the dissenting opinion’s alternative 

interpretation of the word “replace” suffers from the same flaw as 

EPA’s interpretation. A manufacturer “provides a substitute for” an 

ozone-depleting substance in a product when the manufacturer 

transitions to making that product with a substitute substance. After 

that transition takes place, the manufacturer can no longer “provide 

a substitute for” an ozone-depleting substance. At that point, there 

is no ozone-depleting substance to “provide a substitute for.” 

Therefore, even under the dissenting opinion’s interpretation, a 

manufacturer cannot “replace” an ozone-depleting substance after 

the manufacturer stops using that substance. 
15

manufacturer’s use of that substitute. That boundless 

interpretation of EPA’s authority under Section 612(c) borders 

on the absurd.

Because the text is sufficiently clear, we need not consider 

the legislative history. See NLRB v. SW General, Inc., 137 S. 

Ct. 929, 942, slip op. at 14 (2017). In any event, the legislative 

history strongly supports our conclusion that Section 612(c) 

does not grant EPA continuing authority to require replacement 

of non-ozone-depleting substitutes. The Senate’s version of 

Title VI applied to “Stratospheric Ozone and Global Climate 

Protection.” S. 1630, 101st Cong. tit. VII (as passed by Senate, 

Apr. 3, 1990) (emphasis added). The Senate’s version of the 

safe alternatives policy would have required the replacement 

not just of ozone-depleting substances, but also of substances 

that contribute to climate change. Id. sec. 702, §§ 503(8), 

514(a). In other words, the Senate bill would have granted 

EPA authority to require the replacement of non-ozonedepleting substances such as HFCs. But the Conference 

Committee did not accept the Senate’s version of Title VI. See 

H.R. Rep. No. 101-952, at 262 (1990) (Conf. Rep.). Instead, 

the Conference Committee adopted the House’s narrower 

focus on ozone-depleting substances. Id.; see S. 1630, 101st 

Cong. sec. 711, § 156(b) (as passed by House, May 23, 1990). 

In short, although Congress contemplated giving EPA broad 

authority under Title VI to regulate the replacement of 

substances that contribute to climate change, Congress 

ultimately declined.

Put simply, EPA’s strained reading of the term “replace”

contravenes the statute and thus fails at Chevron step 1. And 

even if we reach Chevron step 2, EPA’s interpretation is 

unreasonable. See Chevron U.S.A. Inc. v. Natural Resources 

Defense Council, Inc., 467 U.S. 837, 843 & n.9 (1984); see also 
16

Global Tel*Link v. FCC, 859 F.3d 39, 59-60 (D.C. Cir. 2017) 

(Silberman, J., concurring).

Notwithstanding our conclusion regarding Section 612, 

EPA still possesses several statutory authorities to regulate 

HFCs. 

For one thing, EPA has statutory authority under Section 

612(c) to prohibit any manufacturers that still use ozonedepleting substances that are covered under Title VI from 

deciding in the future to replace those substances with HFCs. 

Those manufacturers have yet to “replace” ozone-depleting 

substances with a substitute. When they ultimately do replace 

ozone-depleting substances, EPA may prohibit them from 

using HFCs as substitutes.5

For another thing, EPA possesses other statutory 

authorities, including the Toxic Substances Control Act, to 

directly regulate non-ozone-depleting substances that are 

causing harm to the environment. See 15 U.S.C. §§ 2601-2629 

(Toxic Substances Control Act); see also 42 U.S.C. § 7408 

(National Ambient Air Quality Standards program); id. § 7412 

(Hazardous Air Pollutants program); id. §§ 7470-7492 

(Prevention of Significant Deterioration program); id. § 7521 

(Section 202 of Clean Air Act). Our decision today does not in 

any way cabin those expansive EPA authorities.

In addition, EPA still has statutory authority to require 

product manufacturers to replace substitutes that (unlike HFCs)

are themselves ozone depleting. See, e.g., 42 U.S.C. §§ 7671c, 

 

5 To be sure, Mexichem and Arkema argue that EPA acted 

arbitrarily and capriciously in removing HFCs from the list of safe 

substitutes. As explained in Part III below, however, we reject that 

argument. We conclude that EPA acted lawfully in removing HFCs 

from the list of safe substitutes.
17

7671d. Suppose, for example, that EPA determines that a 

substance is a safe substitute for ozone-depleting substances, 

but EPA later concludes that the substitute is itself an ozonedepleting substance that is covered under Title VI. In that 

circumstance, EPA possesses statutory authority to order the 

replacement of that ozone-depleting substance in accordance 

with the timelines prescribed by Title VI. 

However, EPA’s authority to regulate ozone-depleting 

substances under Section 612 and other statutes does not give 

EPA authority to order the replacement of substances that are 

not ozone depleting but that contribute to climate change. 

Congress has not yet enacted general climate change

legislation. Although we understand and respect EPA’s 

overarching effort to fill that legislative void and regulate 

HFCs, EPA may act only as authorized by Congress. Here, 

EPA has tried to jam a square peg (regulating non-ozonedepleting substances that may contribute to climate change) 

into a round hole (the existing statutory landscape). 

The Supreme Court cases that have dealt with EPA’s 

efforts to address climate change have taught us two lessons 

that are worth repeating here. See, e.g., Utility Air Regulatory 

Group v. EPA, 134 S. Ct. 2427 (2014). First, EPA’s wellintentioned policy objectives with respect to climate change do 

not on their own authorize the agency to regulate. The agency 

must have statutory authority for the regulations it wants to 

issue. Second, Congress’s failure to enact general climate 

change legislation does not authorize EPA to act. Under the

Constitution, congressional inaction does not license an agency 

to take matters into its own hands, even to solve a pressing 

policy issue such as climate change. Justice Breyer has 

summarized that separation of powers point in another

context – there, the war against al Qaeda. See Hamdan v. 

Rumsfeld, 548 U.S. 557, 636 (2006) (Breyer, J., concurring). 
18

Justice Breyer stated in Hamdan that war is not a blank check 

for the President. Id.; see also Youngstown Sheet & Tube Co. 

v. Sawyer, 343 U.S. 579, 637 (1952) (Jackson, J., concurring). 

So too, climate change is not a blank check for the President. 

Those bedrock separation of powers principles undergird

our decision in this case. However much we might sympathize 

or agree with EPA’s policy objectives, EPA may act only 

within the boundaries of its statutory authority. Here, EPA 

exceeded that authority. 

B

EPA’s reliance on the statutory term “replace” does not 

justify the 2015 Rule. But that is not necessarily the end of the 

matter. EPA suggests that it may be able to require 

manufacturers to replace HFCs under an alternative theory. 

The question under that alternative theory is this: May EPA

retroactively conclude that a manufacturer’s past decision to 

“replace” an ozone-depleting substance with HFCs is no longer 

lawful, even though the original replacement with HFCs was 

lawful at the time it was made? Under such a “retroactive 

disapproval” approach, EPA could prohibit manufacturers

from making products that use HFCs even though those HFCs 

were deemed safe substitutes at the time the manufacturers

decided to initially replace an ozone-depleting substance with 

HFCs. 

EPA’s brief to this Court advanced such an argument only 

in passing. In its brief, EPA stated: An “agency’s inherent 

authority to revise an earlier administrative determination 

where faced with new developments or in light of 

reconsideration of the relevant facts is an essential part of the 

office of a regulatory agency.” EPA Br. 27 (internal quotation 

marks omitted). 
19

The problem for present purposes is that EPA did not 

squarely articulate a “retroactive disapproval” rationale in the 

2015 Rule. Instead, EPA relied on its expansive interpretation 

of the word “replace” in the Rule. Therefore, we may not

uphold the Rule based on the “retroactive disapproval” theory. 

See SEC v. Chenery Corp., 332 U.S. 194, 196 (1947); 

Pasternack v. National Transportation Safety Board, 596 F.3d 

836, 838 (D.C. Cir. 2010). 

Rather, we must remand to EPA. On remand, if EPA 

decides to pursue this “retroactive disapproval” approach, the 

agency would have to address at least three issues.

First, for this “retroactive disapproval” theory to hold up, 

EPA would have to reasonably conclude either (i) that Section 

612(c) provides EPA with statutory authority to employ a 

“retroactive disapproval” approach or (ii) that EPA has 

inherent authority to retroactively disapprove a prior 

replacement, even a replacement that occurred many years ago. 

See generally Vartelas v. Holder, 566 U.S. 257, 266 (2012) 

(retroactivity principles in statutory interpretation); Ivy Sports 

Medicine, LLC v. Burwell, 767 F.3d 81, 86 (D.C. Cir. 2014) 

(scope of agencies’ inherent reconsideration authority). 

Second, if EPA concludes that it has authority for 

“retroactive disapprovals,” EPA must explain the basis for its 

conclusion and explain its change in interpretation of Section 

612(c). See FCC v. Fox Television Stations, Inc., 556 U.S. 502, 

515 (2009). As noted above, before the 2015 Rule, EPA 

indicated that Section 612(c) “does not authorize EPA to 

review substitutes for substances that are not themselves” 

covered ozone-depleting substances. EPA Response to 

Comments on 1994 Significant New Alternatives Policy Rule, 

J.A. 50; see Protection of Stratospheric Ozone, 59 Fed. Reg. 
20

13,044, 13,052 (Mar. 18, 1994); EPA Response to OZ 

Technology’s Section 612(d) Petition, J.A. 145. But under the 

retroactive disapproval approach, EPA would in effect require 

manufacturers to replace their HFCs, which are not ozonedepleting substances, with other substitutes. Such a change in 

EPA’s approach would require an explanation. Moreover, to 

the extent that EPA’s prior approach had “engendered serious 

reliance interests,” EPA would need to provide a “more 

detailed justification” for its change. Fox, 556 U.S. at 515.

Third, even if EPA has authority for a “retroactive 

disapproval” approach, EPA must comply with applicable due 

process constraints on retroactive decisionmaking. The Due 

Process Clause limits the Government’s authority to

retroactively alter the legal consequences of an entity’s or 

person’s past conduct. To satisfy the Due Process Clause, EPA 

must at a minimum “provide regulated parties fair warning of 

the conduct a regulation prohibits or requires.” Christopher v. 

SmithKline Beecham Corp., 567 U.S. 142, 156 (2012) (internal 

quotation marks and alteration omitted). In this case, for 

example, even if EPA has statutory authority to retroactively 

disapprove the replacement of an ozone-depleting substance 

with HFCs, EPA plainly may not impose civil or criminal 

penalties on a manufacturer based on the manufacturer’s past

use of HFCs at the time when EPA said it was lawful to use 

HFCs. See id. We do not understand EPA to disagree with that 

proposition. 

Unless and until EPA concludes on remand that it has 

cleared those three hurdles,

6 EPA may not apply the 2015 Rule 

 

6 We take no position now on whether EPA can meet those 

requirements. Moreover, we note that those three requirements 

would be necessary for EPA to prevail on a “retroactive disapproval” 

theory. We do not opine here on whether they would be sufficient.
21

to require manufacturers to replace one non-ozone-depleting 

substitute with another substitute, so long as the initial 

substitute was listed as safe at the time the substitution was 

effectuated. Of course, even if EPA concludes that it has 

cleared those hurdles, EPA’s conclusions may be subject to 

review in this Court in another case. 

In short, we vacate the 2015 Rule to the extent the Rule 

requires manufacturers to replace HFCs with a substitute 

substance. We remand to EPA. On remand, if it chooses, EPA 

may determine whether it has “retroactive disapproval” 

authority – whether, in other words, it has authority to conclude 

that a manufacturer’s past decision to replace an ozonedepleting substance with HFCs is no longer lawful.

III

Our conclusion that the 2015 Rule must be vacated to the 

extent it requires manufacturers to replace HFCs does not 

answer the question whether EPA reasonably removed HFCs 

from the list of safe substitutes in the first place. Mexichem 

and Arkema assert that EPA’s decision to remove HFCs from 

the list of safe substitutes was arbitrary and capricious. In 

support, they advance a number of arguments. 

The arbitrary and capricious standard requires that a rule 

be “reasonable and reasonably explained.” Communities for a 

Better Environment v. EPA, 748 F.3d 333, 335 (D.C. Cir. 2014) 

(internal quotation marks omitted). EPA must “examine the 

relevant data and articulate a satisfactory explanation for its 

action.” Motor Vehicle Manufacturers Association of United 

States, Inc. v. State Farm Mutual Automobile Insurance Co., 

463 U.S. 29, 43 (1983). Applying that deferential standard, we 

reject all of Mexichem and Arkema’s arbitrary and capricious 

challenges. 
22

First, Mexichem and Arkema assert that EPA ignored a 

key “requirement” in the 1994 Rule implementing Section 

612(c) – namely, that EPA may “restrict only those substitutes 

that are significantly worse” than the available alternatives. 

Reply Br. 21; Protection of Stratospheric Ozone, 59 Fed. Reg. 

13,044, 13,046 (Mar. 18, 1994) (capitalization altered). They 

claim that EPA did not demonstrate that HFCs are significantly 

worse than the available alternatives. In fact, however, the 

1994 Rule said that restricting significantly worse substitutes 

was just one of seven “guiding principles” for EPA – not a 

hard-and-fast requirement. Protection of Stratospheric Ozone, 

59 Fed. Reg. at 13,046. Moreover, based on data regarding the 

environmental effects of the relevant substances, EPA 

repeatedly concluded that the substances EPA added to the list 

of prohibited substitutes posed a “significantly greater risk” 

than the available alternatives. See, e.g., Final Rule, 80 Fed. 

Reg. at 42,904, 42,905, 42,912, 42,915, 42,917, 42,919. So 

that challenge fails.7

Second, Mexichem and Arkema argue that EPA should not 

have relied so heavily on the numeric Global Warming 

Potential score to assess the “Atmospheric effects and related 

health and environmental impacts” of HFCs and other 

substitutes. 40 C.F.R. § 82.180(a)(7)(i). But as EPA has 

explained, that is the tool preferred by leading scientists for 

analyzing the effects of greenhouse gases. EPA Response to 

 

7 Mexichem and Arkema also assert that EPA’s decision to 

change the listing status of HFCs violated EPA’s regulations because 

EPA did not compare HFCs to the proper comparator substances. 

See 40 C.F.R. §§ 82.170(a), 82.172. That is not accurate. In the 2015 

Rule, EPA compared HFCs with other substances that are on EPA’s 

list of safe substitutes, as EPA is permitted to do under its 

regulations. See id. § 82.170(a); Final Rule, 80 Fed. Reg. at 42,937. 
23

Comments on Proposed Rule at 162, J.A. 727. EPA reasonably 

relied on the Global Warming Potential score. 

Third, Mexichem and Arkema suggest that EPA failed to 

provide objective benchmarks for determining which 

substances’ Global Warming Potential scores were too high to 

be acceptable. But EPA was not assessing the score of each 

individual substance in isolation. Instead, EPA was comparing

substances with one another. EPA reasonably concluded that 

substances with higher scores posed a greater global warming 

risk than substances with lower scores. See, e.g., Final Rule, 

80 Fed. Reg. at 42,882. That is a “comprehensible” and 

objective method for assessing environmental risks. Postal 

Service v. Postal Regulatory Commission, 785 F.3d 740, 753 

(D.C. Cir. 2015). 

Fourth, according to Mexichem and Arkema, EPA failed 

to consider data regarding the overall amount of each substitute 

that would be emitted into the atmosphere. Not so. EPA 

considered whether there were “substantial differences” 

between HFCs and other substitutes that “might affect total 

atmospheric emissions.” Final Rule, 80 Fed. Reg. at 42,938. 

EPA also looked at other factors related to atmospheric 

emissions, “such as charge size of refrigeration equipment and 

total estimates of production,” as part of “its assessment of 

environmental and health risks of new alternatives.” Id. 

Because EPA accounted for factors that affect the quantity of 

emissions, EPA did not entirely fail to “consider an important 

aspect of the problem.” State Farm, 463 U.S. at 43. 

Fifth, Mexichem and Arkema assert that EPA should have 

accounted for energy efficiency when assessing the 

atmospheric effects of HFCs. But as EPA explained, the 

energy efficiency of a substance often is not informative in 

isolation. Final Rule, 80 Fed. Reg. at 42,921-22. The 
24

efficiency of the substance depends on the efficiency of the 

equipment in which the substance is used. In part because EPA 

cannot control the efficiency of equipment under Section 

612(c), EPA decided not to evaluate the energy efficiency of 

substitutes in its analysis. Id. Under those circumstances, 

EPA’s approach was reasonable and reasonably explained.

Sixth, Mexichem and Arkema argue that EPA should have 

placed conditions on how HFCs could be used, rather than 

entirely prohibiting certain uses of HFCs. But EPA adequately 

explained that use controls are typically appropriate when a 

particular use of a substance carries an especially high risk that

can be mitigated by placing conditions on that use. Id. at 

42,899. Use controls would not be appropriate for HFCs, EPA 

stated, because the hazards of HFCs are not unique to particular 

uses. Instead, “the environmental risks” from HFCs “are due 

to the collective global impact of refrigerant emissions released 

over time.” Id. EPA also explained that use controls for HFCs 

did not make sense because other substitutes are readily 

available. Id. That conclusion is reasonable and reasonably 

explained for purposes of arbitrary and capricious review under 

the Administrative Procedure Act.

Seventh, Mexichem and Arkema claim that EPA failed to 

consider transition costs – that is, the costs of transitioning 

from prohibited HFCs to approved substitutes. But EPA did 

take transition costs into account when it decided to give 

certain product manufacturers extra time to comply with the 

Rule. See, e.g., id. at 42,933. EPA acted reasonably for 

purposes of arbitrary and capricious review. 

* * *

In sum, we grant the petitions and vacate the 2015 Rule to 

the extent it requires manufacturers to replace HFCs with a 
25

substitute substance. We remand to EPA for further 

proceedings consistent with this opinion. We reject all of 

Mexichem and Arkema’s other challenges to the 2015 Rule. 

The petitions are therefore granted in part and denied in part. 

So ordered.
WILKINS, Circuit Judge, concurring in part and dissenting 

in part: I must depart from the Court’s opinion concluding that 

Section 612 of the Clean Air Act unambiguously prohibits EPA 

from requiring the replacement of HFCs. The majority claims 

that “EPA’s novel reading of Section 612 is inconsistent with 

the statute as written,” because Section 612 does not provide 

EPA with the authority to require “manufacturers to replace 

non-ozone-depleting substances such as HFCs.” Maj. Op. 3. 

Accordingly, the majority disposes of the issue in a Chevron 

step-one analysis through an interpretation of the word 

“replace.” See id. at 9-15. I disagree. The bar for deciding a 

case at Chevron step one is high, requiring clear and 

unambiguous congressional intent. See Chevron, U.S.A., Inc. 

v. Nat. Res. Def. Council, Inc., 467 U.S. 837, 843 (1984).

Because the term “replace” is susceptible of multiple

interpretations in this context, it cannot serve as the basis for 

discerning clear congressional intent. See, e.g., U.S. Postal 

Serv. v. Postal Regulatory Comm’n, 640 F.3d 1263, 1267 n.4 

(D.C. Cir. 2011) (“Our second inquiry will require us to 

proceed to Chevron step 2 because the phrase ‘due to’ has an 

additional—and ambiguous—meaning, which the Commission 

did not address.”). Thus, the Court must proceed to Chevron 

step two and decide whether EPA’s interpretation of the 

statutory scheme is reasonable. Because I find that it is, I 

would deny the petition on all grounds. 

I.

We review EPA’s interpretation of the Clean Air Act 

under the two-step framework established in Chevron. See 

Catawba Cnty., N.C. v. EPA, 571 F.3d 20, 35 (D.C. Cir. 2009). 

Pursuant to step one of the Chevron analysis, “both the agency 

and the courts [must] give effect to Congress’s unambiguously 

expressed intent if the underlying statute speaks directly to the 

precise question at issue.” Citizens of Coal Council v. Norton, 

300 F.3d 478, 481 (D.C. Cir. 2003). In other words, “if the 
2

intent of Congress is clear and unambiguously expressed by the 

statutory language at issue, that would be the end of our 

analysis.” Zuni Pub. Sch. Dist. No. 89 v. Dep’t of Educ., 550 

U.S. 81, 93 (2007). When making this determination, we may

rely on the traditional tools of statutory interpretation, 

including the statute’s text, structure, purpose, and legislative 

history. Citizens of Coal Council, 300 F.3d at 481. 

I respectfully disagree with the majority that the relevant 

language in Section 612 meets the Chevron step one standard.

This is simply not a case where Congress has clearly and 

directly spoken to the issue in a manner that “unambiguously 

foreclosed the agency's statutory interpretation.” Catawba 

Cnty., 571 F.3d at 35.

The majority focuses primarily upon two provisions of 

Section 612 as clearly and unambiguously demonstrating that 

the 2015 Rule was not authorized by Congress. Here are the 

two provisions:

To the maximum extent practicable, class I and 

class II substances shall be replaced by 

chemicals, product substitutes, or alternative 

manufacturing processes that reduce overall 

risks to human health and the environment. 

42 U.S.C. § 7671k(a) (emphasis added).

Within 2 years after November 15, 1990, the 

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, 
3

where the Administrator has identified an 

alternative to such replacement that—

(1) reduces the overall risk to human health 

and the environment; and

(2) is currently or potentially available.

The Administrator shall publish a list of (A) the 

substitutes prohibited under this subsection for 

specific uses and (B) the safe alternatives 

identified under this subsection for specific 

uses. 

Id. § 7671k(c) (emphasis added).

The majority contends that the word “replace,” when used 

in these two provisions, can have only one meaning: to “take 

the place of.” Maj. Op. 13-14; see id. at 14 (“In common 

parlance, the word ‘replace’ refers to a new thing taking the 

place of the old.”). Under this definition, a substitute can only 

“replace” an ozone-depleting substance once. After the 

manufacturer has transitioned from an ozone-depleting 

substance to a non-ozone-depleting substitute, there is nothing 

left to “replace.” Id. While the majority’s definition may be 

one way to interpret the statute, for several different reasons, it 

is by no means the only way to construe the text. 

First, with respect to the plain text of the statute, the 

meaning of the word “replace” is ambiguous. Nowhere in 

Section 612 is the term “replace” statutorily defined. See 42 

U.S.C. § 7671 (definitions). The majority does not disagree, 

and instead relies on dictionary definitions to conclude that 

“replace” means to “take the place of.” Maj. Op. 13-14. 

However, each of the dictionaries cited by the majority also 

defines “replace” to mean to “substitute for.” See THE 

AMERICAN HERITAGE DICTIONARY OF THE ENGLISH 

LANGUAGE (5th ed. 2017 online) (“To fill the place of; provide 
4

a substitute for”); WEBSTER’S THIRD NEW INTERNATIONAL 

DICTIONARY 1925 (1993) (“[T]o take the place of: serve as a 

substitute for or successor of”); THE OXFORD ENGLISH 

DICTIONARY 642 (2d ed. 1989) (“To take the place of, become 

a substitute for (a person or thing).”). 

The difference in meaning between “to take the place of” 

and “to provide a substitute for” may be subtle, but it is rather

significant in the context of this statute. Section 612 pertains 

to replacing a category, or class, of chemical substances; 

indeed the substances are defined in the statute as “class I” and 

“class II” substances. 42 U.S.C. § 7671(3), (4). Thus, this 

statute is not directed to a specific individual or position, and 

the majority’s example noting that “President Obama replaced

President Bush at a specific moment in time,” Maj. Op. 14, is 

therefore inapposite. A more pertinent example would be: 

“Hybrid electric engines, fully electric engines, hydrogen fuel 

cell power, and other alternatives are replacing the internal 

combustion engines in passenger cars.” The Oxford Dictionary 

provides a similar example sentence: “This is required to 

replace older medicines that will eventually face competition 

from generic substitutes.” Replace, OXFORD DICTIONARY, 

https://en.oxforddictionaries.com/definition/replace (last 

accessed July 14, 2017). In both examples, the ubiquitous 

product that has become the industry standard is “replaced” by 

a number of substitutes, and the replacement takes place not at 

a specific point in time, not just once, and not by a single 

substitute. Instead, the ubiquitous item is “replaced” by any 

number of substitutes over the course of years, and it may be 

the case that one substitute is succeeded by a better substitute 

at some point in time. As one dictionary puts it, “Replace

applies both to substituting something new or workable for that 

which is lost, depleted or won out and to placing another in the 

stead of one who leaves or is dismissed from a position.” 

American Heritage Dictionary (2d Coll. ed. 1982).
5

Second, the structure of the statutory text also contradicts 

the clear meaning proffered by the majority. The two key 

provisions of Section 612 are not directed to any particular 

group of individuals or class of companies. They provide that 

“class I and class II substances shall be replaced by chemicals, 

product substitutes, or alternative manufacturing processes,” 

42 U.S.C. § 7671k(a), and that “it shall be unlawful to replace 

any class I or class II substance with any substitute substance,” 

id. § 7671k(c). These Congressional mandates, written in the 

passive voice and without identifying a particular target of the 

regulation, appear to apply to anyone and everyone, including 

retailers, product manufacturers and chemical manufacturers.1 

The majority focuses on product manufacturers, contending 

that once the manufacturer replaces the class I or class II 

substance in its product with a non-ozone-depleting substitute, 

“the replacement has been effectuated.” Maj. Op. 14. 

However, this point of view ignores the retailer. Suppose 

a retailer needs to refurbish an air conditioner manufactured in 

the early 1990s that uses a class I substance as a refrigerant. If 

the retailer chooses to have the air conditioner serviced by 

recharging it with new refrigerant, she is prohibited from 

 

1

In other provisions of Section 612, Congress identified the target of 

the regulation as chemical manufacturers, like the petitioners in this 

case. See, e.g., 42 U.S.C. § 7671(e) (“The Administrator shall 

require any person who produces a chemical substitute for a class I 

substance to provide the Administrator with such person's 

unpublished health and safety studies on such substitute and require 

producers to notify the Administrator not less than 90 days before 

new or existing chemicals are introduced into interstate commerce 

for significant new uses as substitutes for a class I substance.”

(emphasis added)); see also id. § 7671(11) (defining “produce” as 

“the manufacture of a substance from any raw material or feedstock 

chemical . . . .”).
6

“replacing” the class I substance with a chemical substitute

“which the Administrator determines may present adverse 

effects to human health or the environment[,]” 42 U.S.C. 

§ 7671k(a). If the retailer chooses to purchase a new air 

conditioner instead, she is still “replacing” a class I substance,

and the new air conditioner cannot contain an unsafe substitute. 

Id. Either way, the retailer’s action falls within the scope of the 

mandates in Section 612. And if the retailer purchases a new 

air conditioner, the fact that the manufacturer may have 

previously “replaced” a class I substance with an HFC as the

refrigerant in its air conditioners does not mean that “the 

replacement has [already] been effectuated” with respect to that 

retailer. See Maj. Op. 14. By the express terms of the statute, 

if the EPA determines as of 2017 that HFCs are no longer safe 

substitutes for class I substances given available refrigerant 

alternatives, it would appear that Congress has given EPA the

authority to prohibit the further use of HFCs in air conditioners 

so that the retailer in our example cannot “replace” her class I 

substance-utilizing air conditioner with a new air conditioner 

utilizing an unsafe substitute. The majority holds otherwise. 

Alternatively, the express terms of the statute appear to give 

EPA the authority to prohibit the retailer from recharging her 

old air conditioner with an HFC as the refrigerant, which the 

agency could implement by restricting the manufacture, 

marketing, and use of HFCs. Given its focus on product 

manufacturers, the majority opinion is curiously silent about 

how its statutory interpretation affects retailers and other end 

users who have products utilizing class I and class II 

substances, despite the obvious importance of the issue.

In my view, the connotation of “replace” as “to provide a 

substitute for” more accurately reflects the intent of Congress

given the use of the term and sentence structure in the key 

statutory provisions. This interpretation is further supported by 

the fact that Congress used the word “substitute” ten separate 
7

times in Section 612, and the word “alternative” a dozen times

more, including in the title of the section. See 42 U.S.C. 

§ 7671k (“Safe Alternatives Policy”). In that context, 

“replacing” the class I or class II substance is not necessarily a 

one-time event and alternatives or substitutes can be deemed 

replacements or successors, even if they are not the firstgeneration successor. At a minimum, the definition of 

“replace” is ambiguous, and “to provide a substitute for” just 

as likely manifests Congress’s intent as the definition proffered 

by the majority. “Confronted by two plausible readings of the 

statute, we cannot declare Congress’ intent unambiguous.” 

Adirondack Med. Ctr. v. Sebelius, 740 F.3d 692, 698 (D.C. Cir. 

2014).

Third, the majority’s interpretation also undermines the 

purpose of Section 612, which is, “[t]o the maximum extent 

practicable,” to carry out the replacement of class I and class II 

substances with “chemicals, product substitutes, or alternative 

manufacturing processes that reduce overall risks to human 

health and the environment.” 42 U.S.C. § 7671k(a). 

Significantly, Congress authorized EPA to develop a list of 

unsafe alternatives and a list of safe alternatives, but Congress 

chose, for whatever reason, only to bar the use of alternatives 

on the “unsafe list,” rather than mandating the use of only those 

alternatives appearing on the “safe list.” See id. § 7671k(c) (“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”). By writing the statute in this manner, Congress 

allowed manufacturers to replace class I and II substances with 

alternatives that have not been specifically approved by the 

EPA, so long as the substitute has not been specifically deemed 

unsafe by the EPA. The majority’s interpretation of “replace” 

makes a mockery of the statutory purpose, because a product 

manufacturer could “replace” a class I substance with a 
8

substitute before the EPA has a chance to evaluate it 

completely, and if the agency later determines that a different

substitute “reduce[s] overall risks to human health and the 

environment,” id. § 7671k(a), the agency would be powerless 

to tell that product manufacturer that it could no longer use the 

more risky substitute. In the majority’s view, the 

“replacement” is a fait accompli, and EPA is powerless to act 

under Section 612. Such an interpretation undermines 

Congress’s intent to “reduce overall risks to human health and 

the environment” in a manner “to the maximum extent 

practicable.” Id. 

In doing so, the majority takes an even more extreme 

position than petitioners, who conceded that “if ozonedepleting substances are in use, EPA can list and de-list” to and 

from the lists of acceptable and unacceptable alternatives. Oral 

Arg. at 11:07, Mexichem Fluor, Inc. v. EPA (Feb. 17, 2017) 

(No. 15-1328). According to petitioners, EPA “can list or delist ozone-depleting substances and non-ozone-depleting 

substances because the list at that point is consisting of things 

that will replace the things that are in use, which are ozonedepleting substances . . . .” Id. at 11:14 (emphasis added). The 

petitioners are at least trying to interpret “replace” in a manner 

consistent with the statutory purpose – but as explained infra

in part II, they are simply wrong on the facts, because ozonedepleting substances are still in use. The majority’s definition 

of “replace,” on the other hand, has no semblance of 

consistency with this aspect of Congress’s purpose.

Indeed, Section 612 is aimed at regulating which 

substitutes can be used as replacements for class I and class II 

substances, rather than regulating those ozone-depleting 

substances themselves. Congress phased out the production 

and manufacture of ozone-depleting substances in other

statutory provisions. See 42 U.S.C. §§ 7671c, 7671d. Section 
9

612, on the other hand, is focused solely on substituting class I 

and class II substances with safe alternatives. See id. § 7671k. 

Because Section 612 promotes the use of safe substitutes, it 

necessarily requires a reading of the word “replace” that 

comports with this congressional intent. The majority’s 

cramped reading of the statute contradicts Congress’s intent 

that the EPA prohibit the use of “any substitute substance” that 

may “present adverse effects to human health and the

environment” where a less risky substitute is available. Id. § 

7671k(c) (emphasis added).

Moreover, the majority’s interpretation also runs counter 

to the purpose of the petition process contained in Section 612. 

Congress provided that “[a]ny person may petition the 

Administrator to add a substance to the [safe or unsafe 

alternatives] lists . . . or to remove a substance from either of 

such lists.” Id. § 7671k(d). The petition process becomes a 

half-measure if EPA is only allowed to “replace” an ozonedepleting substance once and only once. The majority’s 

interpretation grants EPA one bite at the apple, prohibiting

additions to the unsafe substitutes list or removals from the safe 

substitutes list if the product manufacturer has already begun 

using a non-ozone-depleting substitute for the class I or class II 

substance. By creating this petition process, it is evident that 

Congress desired the safe alternatives list to be a fluid and 

evolving concept that promotes those alternatives that pose the 

least overall risk to human health and the environment. 

Congress undoubtedly knew how to instruct EPA to develop a 

list of acceptable and unacceptable substitutes by a certain date 

and then stop there. The fact that Congress did not do so is 

telling. See City of Arlington, Tex. v. FCC, 133 S. Ct. 1863, 

1868 (2013) (“Congress knows to speak in plain terms when it 

wishes to circumscribe, and in capacious terms when it wishes 

to enlarge, agency discretion.”). Congress chose a starkly 

different path, and the majority has taken the power that 
10

Congress granted individuals to request the addition of more 

risky substitutes to the unsafe list and rendered it largely

impotent. When interpreting two interrelated statutory 

provisions, “[a]bsent clearly expressed congressional intent to 

the contrary, it is our duty to harmonize the provisions and 

render each effective.” Adirondack Med. Ctr., 740 F.3d at

698–99.

Fourth, the majority’s references to EPA’s prior 

interpretations of its statutory authority cannot change the

Chevron step one analysis. See Maj. Op. 12. I agree with the 

majority that we must reject any EPA interpretation of 

“replace” if we determine that Congress has clearly and 

directly spoken to the contrary, because “[t]he judiciary is the 

final authority on issues of statutory construction and must 

reject administrative constructions which are contrary to clear 

congressional intent.” Chevron, 467 U.S. at 843 n.9. But the 

EPA’s interpretations of the statute are not themselves suitable

evidence of Congress’s clear intent. See Village of Barrington, 

Ill. v. Surface Transp. Bd., 636 F.3d 650, 660 (D.C. Cir. 2011); 

see also Kentuckians for Commonwealth Inc. v. Rivenburgh, 

317 F.3d 425, 443 (4th Cir. 2003) (“Agency interpretations of 

statutory provisions only come into play if Congress has not 

spoken clearly. Relying on agency interpretations as evidence 

of a clear congressional intent is therefore misguided.”

(emphasis in original)).

Finally, an examination of Section 612’s legislative 

history does not change the outcome. Where “a statute is silent 

or ambiguous with respect to the question at issue,” we must 

“defer to the ‘executive department’s construction of a 

statutory scheme it is entrusted to administer,’ unless the 

legislative history of the enactment shows with sufficient clarity 

that the agency construction is contrary to the will of 

Congress.” Japan Whaling Ass'n v. Am. Cetacean Soc., 478 
11

U.S. 221, 233 (1986) (quoting Chevron, 467 U.S. at 844

(emphasis added, citation omitted)). In other words, 

“conflicting [legislative history] cannot clarify ambiguous 

statutory language,” Am. Bankers Ass'n v. Nat'l Credit Union 

Admin., 271 F.3d 262, 269 (D.C. Cir. 2001), and “[w]hile 

[legislative] history can be used to clarify congressional intent 

even when a statute is superficially unambiguous, the bar is 

high,” Williams Companies v. FERC, 345 F.3d 910, 914 (D.C. 

Cir. 2003). 

Here, the legislative history cited by the majority cannot 

meet the required high bar to show clear Congressional intent, 

particularly since the legislative activity “was not . . . addressed 

to the precise issue raised by th[is] case[].” Chevron, 467 U.S. 

at 853. The precise question presented here is whether 

“Section 612 unambiguously covers only replacements of 

ozone-depleting substances and does not authorize 

‘replacements of replacements’.” Pet’rs’ Br. 29. The Senate 

bill cited by the majority had no provisions whatsoever 

regarding how replacements of covered substances were to be 

carried out. Instead, the Senate bill would have phased out 

production entirely of not only ozone-depleting substances, but 

also certain substances which were known or reasonably 

suspected to contribute to “atmospheric or climatic 

modification.” S. 1630, 101st Cong. §§ 504, 506 (as passed by 

Senate, Apr. 3, 1990). But the Senate bill had no provisions for 

creating a list of acceptable substitutes or for prohibiting

unacceptable substitutes; nor did it have any provisions for 

adding substitutes to, or removing substitutes from, the

“acceptable” and “unacceptable” lists. Instead, the Senate bill 

directed EPA to support programs to identify and promote the 

development of safe alternatives and to maintain a public 

clearinghouse of “available” alternatives. Id. § 514. All of the 

statutory provisions in Section 612 concerning acceptable and 

banned alternatives originated in the House bill. S. 1630, 101st 
12

Cong. § 156 (1990) (as passed by House, May 23, 1990). At 

best, this legislative history shows that Congress rejected a 

proposal to ban and phase out the production of substances that 

contribute to climate change. However, the history is silent on 

the much different question of whether Congress intended to 

allow EPA to make “replacements of replacements” of the 

substitutes for banned ozone-depleting substances. Because 

“the legislative history as a whole is silent on the precise issue 

before us,” Chevron, 467 U.S. at 862, it cannot demonstrate 

clear congressional intent on that question.

* * *

Given my interpretation of Section 612’s plain language, 

purpose, and legislative history, I cannot agree with my 

colleagues that the word “replace” clearly and unambiguously 

means to “take the place of,” and only permits a one-time 

replacement of ozone-depleting substances. Rather, at a 

minimum, sufficient ambiguity exists to proceed to Chevron 

step two. See, e.g., NRDC v. EPA, 22 F.3d 1125, 1138 (D.C. 

Cir. 1994) (“Because the phrase ‘take effect’ is itself 

ambiguous, its meaning must be discerned according to 

Chevron’s second step.”). 

II.

The second step in the Chevron framework requires courts 

to grant deference to an administrative agency’s construction 

of an ambiguous statute if that interpretation is reasonable. 

Chevron, 467 U.S. at 843. “[A] court may not substitute its 

own construction of a statutory provision for a reasonable 

interpretation made by the administrator of an agency.” Id. 

Where the interpretation would be one Congress could have 

sanctioned, the administrative agency is entitled to deference 

and its construction should be afforded “considerable weight.” 

Id.
13

For the reasons discussed in Part I, I find EPA’s 

interpretation of Section 612 to be reasonable. EPA’s 

interpretation comports with a common definition of the word 

“replace,” which is to “[p]rovide a substitute for.” See, e.g., 

Replace, OXFORD DICTIONARY, supra. This meaning of 

“replace” is consistent with Section 612’s statutory purpose, 

which is, “to the maximum extent practicable,” to replace 

ozone-depleting substances with “chemicals, product 

substitutes, or alternative manufacturing processes that reduce 

overall risks to human health and the environment.” 42 U.S.C. 

§ 7671k(a)(emphasis added). Comparing alternatives to each 

other and selecting the alternative that creates the lowest level 

of overall risk to human health and the environment accords 

nicely with the policy choice explicitly stated by Congress. 

EPA’s interpretation further avoids the majority’s 

manufacturer-by-manufacturer structure, which does not fully 

comport with the statutory framework. 

Finally, I do not read the administrative record in the same 

manner as the majority. EPA never stated that regulation of 

non-ozone-depleting substitutes was completely off limits, nor 

clearly acted in a manner to foreclose its present interpretation. 

The past language of EPA that is relied upon by the 

majority is far from conclusive on the meaning of “replace” in 

this context. It is true that EPA stated in the course of the 1994 

rulemaking that “Section 612(c) authorizes EPA to review all 

substitutes to Class I and II substances, but does not authorize 

EPA to review substitutes for substances that are not 

themselves class I or II substances.” J.A. 50. But this excerpt 

alone does not tell the whole story. At the time, several 

commenters requested that “EPA clarify that SNAP should 

only apply to substitutes for Class I or Class II compounds,” 

while another commenter suggested “that SNAP should 

aggressively reevaluate previously approved second-
14

generation alternatives as new and environmentally preferable 

alternatives are developed.” Id. EPA began its response to 

these comments as follows: 

A key issue is whether there exists a point at 

which an alternative should no longer be 

considered a class I or II substitute as defined 

by Section 612. The Agency believes that as 

long as class I or II chemicals are being used, 

any substitute designed to replace these 

chemicals is subject to review under Section 

612. 

J.A. 50 (emphasis added). This statement by the agency is 

consistent with how it has construed “replace” in the 2015 

Rule. 

Furthermore, EPA’s seemingly contradictory statement 

relied upon by the majority must be placed in context. In 

Section 612, Congress specified that producers of chemical 

substitutes for class I substances are required “to provide the

Administrator with such person's unpublished health and safety 

studies on such substitute and require producers to notify the

Administrator not less than 90 days before new or existing 

chemicals are introduced into interstate commerce for 

significant new uses as substitutes for a class I substance.” 42 

U.S.C. § 7671k(e). This advance reporting requirement gives 

the agency a 90-day period to review the chemical substitute 

and related data and make a determination as to whether it is a 

safe alternative or unsafe alternative for a class I or class II 

substance before the substitute hits the marketplace.2 The EPA 

 

2 During the 1994 rulemaking, EPA stated its intent to apply the 90-

day advance reporting requirement to new substitutes for class II 
15

and the National Resources Defense Council contend that 

EPA’s 1994 comment only pertained to the 90-day advance 

reporting – and concomitant – review requirements of the 

SNAP program. Resp’t’s Br. 6; NRDC Intervenor’s Br. 13. 

Thus, when the agency stated that “Section 612(c) authorizes 

EPA to review all substitutes to Class I and II substances, but 

does not authorize EPA to review substitutes for substances 

that are not themselves class I or II substances,” J.A. 50, EPA 

argues it meant only that 1) it could not require 90-day advance 

reporting of intended use and health data for certain secondgeneration substitutes by chemical manufacturers, and 2) the 

agency was not required to conduct an advance review before 

any such second-generation substitute hit the market. Thus, 

EPA contends that it never said, or meant to say, that EPA had 

no power whatsoever to review second-generation substitutes, 

either in response to a petition or on the agency’s own accord. 

While the back and forth in the commentary during the 1994 

rulemaking is not crystal clear, it appears to support the 

interpretation that EPA only intended to disclaim authority to

“review” second-generation substitutes in the 90-day advance 

notification and review context, and only if the first-generation 

substitute was a non-ozone-depleting substance. See id. (“For 

example, if a hydrofluorocarbon (HFC) is introduced as a firstgeneration refrigerant substitute for either a class I (e.g., CFC12) or class II chemical (e.g., HCFC-22), it is subject to review 

 

substances, even though the statute only expressly mentions the 

advance reporting requirement in the context of substitutes for class 

I substances. J.A. 42. This deadline for review following advance 

notice and reporting is the same as in the petition process, where 

Congress required that EPA, within 90 days, to “grant or deny” a 

petition to add a substitute to, or remove a substitute from, either the 

safe alternatives list or the unsafe alternatives list for class I and class 

II substances. 42 U.S.C. § 7671k(d). 
16

and listing under section 612. Future substitutions to replace 

the HFC would then be exempt from reporting under section 

612 because the first-generation alternative did not deplete 

stratospheric ozone.” (emphasis added)).

3

 

The majority also relies upon EPA’s statement in response 

to a 1995 petition by OZ Technology, Maj. Op. 12, but there 

the EPA appears to have disclaimed regulatory authority under 

SNAP if the substance is being proffered as a “legitimate 

substitut[e]” for a non-ozone-depleting substance, rather than 

as a substitute for a class I or class II ozone-depleting 

substance. J.A. 145, 412. EPA exerted regulatory authority 

over the petition because it found that OZ Technology 

submitted its proposed alternative as a substitute for CFC-12, 

an ozone-depleting substance, rather than as a substitute to 

HFC-134a, a non-ozone-depleting substitute. J.A. 412, 415. 

This course of events seems to be consistent with the agency’s 

position here. At any rate, petitioners concede that the HFCs 

they manufacture are substitutes for CFCs, which are ozonedepleting substances. Thus, petitioners do not stand in the 

same shoes as OZ Technology and they have not identified any 

statements where EPA has disclaimed authority to regulate 

HFCs or other direct substitutes for ozone-depleting substances 

such as CFCs. 

I understand (and share) the majority’s concern that the 

Clean Air Act does not grant EPA the authority to take a 

 

3 Similarly, in this same passage, EPA also stated “[w]here secondgeneration substitutes replace first-generation substitutes that are 

themselves ozone-depleters (e.g., HCFCs), these second-generation 

substitutes are bound by the same notification and review 

requirements under section 612 as first-generation substitutes to 

ozone-depleting chemicals.” Id. (emphasis added).
17

completely unbounded approach and thereby regulate 

“substitutes” for class I and class II substances forever. In my 

view, the regulation of substitutes under Section 612 requires 

that the traditional and ubiquitous ozone-depleting substance 

originally utilized for the specific end-use is still in service. 

Without the prerequisite of an ozone-depleting substance, there 

can be nothing for the substitute to “replace.” In other words, 

where ozone-depleting chemicals are no longer in existence or 

in use for a particular industry or end-use, then EPA cannot 

regulate substitutes for those end-uses under Section 612. 

Here, petitioners claim that “class I and class II substances 

have already been replaced” with respect to the 25 end-uses 

addressed in the 2015 Rule. Pet’rs’ Br. 20. In support of this 

assertion, Petitioners rely on two examples. First, Petitioners 

state that in the motor-vehicle air conditioning sector, CFC-12, 

which is an ozone-depleting substance, had historically been 

used. Id. However, Petitioners claim that the record shows that 

by the mid-1990s, use of CFC-12 in the manufacture of new 

cars stopped in the United States, and manufacturers uniformly 

adopted HFC-134a as a substitute. Id. This statement is true

as far as it goes, but it does not show that ozone-depleting 

substances are not still in use in the motor-vehicle air 

conditioning sector. Indeed, the record confirms “some older 

vehicles may still be using CFC-12.” J.A. 815. Thus, we 

cannot conclude that ozone-depleting substances are not still in 

“use” in this sector. 

Second, Petitioners reference the commercial refrigeration 

industry, arguing that because the commercial refrigeration 

industry has “transitioned away” from ozone-depleting 

substances, such substances are no longer in use in this sector. 

See Pet’rs’ Br. 21; J.A. 528. This argument suffers from the 

same flaw as the motor-vehicle air conditioning argument. The 

fact that modern commercial refrigeration systems may not use 
18

ozone-depleting chemicals does not mean that older 

refrigeration systems do not continue to use such substances, 

and the record indicates that ozone-depleting substances

remain in “use” in the commercial refrigeration industry. J.A. 

535. With respect to the other 23 challenged end-uses, 

Petitioners are silent and offer no support to prove that ozonedepleting substances have been completely eliminated in those 

sectors. 

EPA responds to Petitioners’ claim, arguing that “ozonedepleting substances are still being directly ‘replaced’ by 

approved alternatives,” Resp’t’s Br. 21 n.8, and that “as long 

as ozone-depleting substances are being used, any substitute 

designed to replace these chemicals is subject to review” under 

Section 612, id. at 31 (alterations omitted). While EPA 

acknowledges that “in some cases the use of ozone-depleting 

substances has ceased,” it contends that ozone-depleting 

substances have not been completely eliminated such that a 

“second-generation substitute world” exists. Id. Petitioners 

failed to respond to this argument in their reply brief. Given 

that the burden is on Petitioners to demonstrate that EPA’s 

interpretation of Section 612 is unreasonable or statutorily 

impermissible with respect to these 25 end-uses, they have 

failed to show that the agency’s policy choice “runs counter to 

the evidence before the agency, or is so implausible that it 

could not be ascribed to a difference in view or the product of 

agency expertise.” Mtr. Vehicle Mfrs. Ass'n of the U.S., Inc. v. 

State Farm Mut. Auto. Ins., 463 U.S. 29, 43 (1983). 

***

In sum, I disagree with the majority’s holding in Part II, 

and concur with all remaining parts. I would find the word 

“replace” sufficiently ambiguous to require a Chevron step two

analysis. Because I find that EPA’s interpretation of Section 
19

612 is reasonable, I would deny the petition for review on all 

grounds.