President Trump announced on June 1, 2017, that the United States would withdraw from the Paris

Agreement, without specifying the mechanism for doing so or the date of withdrawal. News reports indicated that the President's advisers, particularly Mssrs. Bannon and Pruitt, were concerned that the Paris Agreement would trigger mandatory greenhouse gas reduction requirements under the Clean Air Act. The  Counsel's Office reportedly had advised that because the decision in Murray v. Schooner Charming Betsy, 6 U.S. 64 (1804), requires the United States to interpret its laws consistent with "the law of nations," the Paris Agreement would result in an interpretation of the Clean Air Act requiring actions to reduce greenhouse gas emissions to the levels necessary to keep temperature increases below 2° C (3.6° F).  

Although the matter will be intensely litigated, there are significant arguments suggesting that the withdrawal cannot be legally effected in a meaningful time frame, if ever, and, even if the withdrawal becomes effective, it would not prevent application of these mandatory requirements under the Clean Air Act. Even if the withdrawal goes into effect, it may have the unintended consequence of triggering less flexible requirements under the Clean Air Act by requiring the development of a National Ambient Air Quality Standard (NAAQS). Although the Trump administration would not willingly promulgate an NAAQS, it can be compelled to do so by way of a citizen suit brought by states, cities, individuals, or organizations. On the other hand, the withdrawal announcement could also have the unintended consequence of directing investment in emerging energy technologies away from the United States.^[1] The President's action has also motivated a number of states and cities to pledge their commitment to achieving the goals of the Paris Agreement and appears to have reenergized these states and cities to pursue their own policies to limit greenhouse gas emissions.

I.      Limitations on the Effect of the Announced Withdrawal from the Paris Agreement

The United States does not have unlimited discretion to withdraw from an international agreement such as the Paris Agreement. Under international law, a state may not "invalidate its consent to be bound by an agreement" unless (a) there was an error of fact, a change in circumstances essential to the parties’ consent, or fraud or corruption; or (b) if the agreement is void because it was procured by corruption or is inconsistent with an international norm. Restatement of the Law, The Foreign Relations Law of the United States (“Restatement”), § 331. A nation may also withdraw from an agreement either in conformity with that agreement or by the consent of the parties. Id. § 332. Article 28 of the Paris Agreement provides that no party may withdraw from the Agreement for at least three years from its effective date, and that withdrawal will not take effect until a year after notice is provided. Thus, under the terms of the Agreement, the United States will not be able to provide official, binding notice of withdrawal until November 4, 2019, and the withdrawal will not take effect until November 4, 2020. 

Moreover, the Paris Agreement merely interprets the intent of the 1993 United Nations Framework Convention on Climate Change (UNFCCC), which the United States ratified after the President received the advice and consent of the Senate, and the Paris Agreement imposes no enforceable obligations beyond those in the UNFCCC. The Paris Agreement defines the goal of the UNFCCC to prevent "dangerous anthropogenic interference with the climate system"^[2] by specifying that achieving this goal requires holding the increase in the global average temperature to well below 2 °C above pre-industrial levels^[3] and decarbonization of the entire world economy by the second half of the 21^st century.^[4]  The Paris Agreement’s provisions for submitting and updating "nationally determined contributions" (NDCs) every five years beginning in 2020^[5] do not add any new requirements for the United States that are not self-selected. They merely give greater definition to the existing UNFCCC obligation for all parties to develop and implement "programmes containing measures to mitigate climate change by addressing anthropogenic emissions," UNFCCC, art. 4, § 1(b), and the obligation for every developed nation to "adopt national policies and take corresponding measures on the mitigation of climate change, by limiting its anthropogenic emissions of greenhouse gases and protecting and enhancing its greenhouse gas sinks and reservoirs." Id. § 2(a).  

Thus, withdrawal from the Paris Agreement by itself would arguably have no effect on the UNFCCC obligation to reduce emissions unless the United States also withdraws from the UNFCCC. Article 25 of the UNFCCC authorizes any party to withdraw from the UNFCCC by providing notice to all other parties, and the withdrawal will take place within one year. It is even unclear whether President Trump could effect a more rapid withdrawal by withdrawing from the UNFCCC. There is an argument that the Paris Agreement's withdrawal terms now apply to the UNFCCC. Moreover, ambiguous legal precedent and the words of the Constitution suggest that there is a colorable question as to whether President Trump could withdraw from the UNFCCC, which was adopted with the consent of the Senate, without the further advice and consent of the Senate, pursuant to art. II, § 2, cl. 2 of the Constitution, although the question could evade judicial review. See, Goldwater v. Carter, 481 F. Supp.  949 (D.D.C.) (holding that Senate consent is required, stating “[l]ike treaty formation, treaty termination is comprised of a series of acts that seek to maintain a constitutional balance), rev’d, 617 F.2d. 697 (D.C. Cir.) (holding en banc that President has power to withdraw without consent), vacated, 444 U.S. 996 (1979) (vacated for lack of jurisdiction, with four justices concurring based on the political question doctrine, one holding the issue was not ripe, one giving no reason, and one holding that it was within the President’s power to withdraw without consent).^[6]

If President Trump withdraws from both the Paris Agreement and the UNFCCC and the Senate’s consent is not required, there are still arguments that withdrawal may not eliminate the effect of the UNFCCC, which could still be considered customary international law binding on the United States.  Some international agreements "may come to be law for non-parties that do not actively dissent."  Restatement, § 102, comment

i. "If an international agreement is declaratory of, or contributes to, customary law, its termination by the parties does not of itself affect the continuing force of those rules as international law."  Id.  See, Restatement, § 102, n. 5; North Sea Continental Shelf Cases (Federal Republic of Germany v. Denmark & Netherlands), 1969 I.C.J. 3,

28-29, 37-43 (Judgment of 20 Feb. 1969); Case Concerning Delimitation of the Maritime Boundary of the Gulf of Maine (Canada/United States), 1984 I.C.J. 246, 294 (Judgment of 12 Oct. 1982). This can be significant with respect to interpretation of the Clean Air Act, since it is a long-standing principle that statutes should be construed consistent with the "law of nations." Murray v. Schooner Charming Betsy, 6 U.S. 64, 118 (1830).

II.    Potential Mandatory Duty to Keep Temperature Increases Below 2° C

There are two sections of the Clean Air Act that arguably create a mandatory duty for EPA to require an economy-wide regulatory program with the aim of reducing greenhouse gas (GHG) emissions commensurate with the goals of the UNFCCC and the Paris Agreement. First, there is arguably a mandatory duty for EPA to list GHGs as criteria pollutants under section 108 of the Act, 42 U.S.C. § 7408, in which case EPA would be required to establish an NAAQS under section 109, id. § 7409, and then issue a directive for all states to develop and submit state implementation plans (i.e. a "SIP call") under section 110, id., § 7410, requiring the states to create economy-wide emissions control programs consistent with the Paris goals. Alternatively, under Section 115 of the Clean Air Act, id.§ 7415, EPA could have a mandatory duty to issue a similar SIP call to address the international impacts of domestically produced greenhouse gas emissions and to meet international goals under the Paris Agreement and the UNFCCC. EPA explored both approaches in the

Advance Notice of Proposed Rulemaking regarding regulation of GHGs under the Clean Air Act.^[7] Moreover, pending petitions request that EPA initiate rulemaking and issue a SIP call under these authorities.^[8] Because the EPA Administrator’s duty in each case is mandatory, the petitioners or other parties can potentially file a citizen suit under the Clean Air Act, 42 U.S.C. § 7504(a), to obtain a court order requiring EPA to take action under either or both sections. The mandatory duty under both sections has arguably been triggered by EPA's finding, affirmed by the D.C. Circuit Court of Appeals, that greenhouse gas emissions endanger public health and welfare, but the prerequisites for triggering the section 115 mechanism also include reciprocal treaty obligations, such as the Paris Agreement. The section 115 mechanism arguably provides greater flexibility in some respects than does the NAAQS mechanism. Therefore, if the withdrawal from the Paris Agreement becomes effective, it could remove the more flexible approach and could subject U.S. states and industry to more stringent requirements than would pertain under section 115 and the Paris Agreement.

Specifically, section 108 of the Clean Air Act creates a mandatory duty requiring that EPA list and promulgate an NAAQS under section 109 for "each air pollutant" whose emissions (1) meet the endangerment standard already found by EPA, (2) arise "from numerous or diverse mobile or stationary sources," and (3) "for which air quality criteria had not been issued before December 31, 1970, but for which [EPA] plans to issue air quality criteria under this section." In the case of lead, EPA was ordered in a citizen suit to list lead and to establish an NAAQS based on the agency prior endangerment finding and the undisputed fact that lead arose from multiple sources. NRDC v. Train, 545 F.2d 320 (2d Cir. 1976). The court rejected EPA’s argument that the language "for which [EPA] intends" gave the EPA discretion not to issue air quality criteria and therefore discretion not to promulgate an NAAQS. EPA’s endangerment finding for GHGs^[9]—coupled with its regulation of GHG emissions from light duty vehicles, heavy duty vehicles, the Clean Power Plan, its intent to regulate methane from multiple sources, and its establishment of guidelines for establishing case-by-case emissions limits under the new source review program—appear to make the case for listing GHGs more compelling than the case presented for lead, since these actions, as well as the various IPCC reports, might be considered the equivalent of air quality criteria.^[10] 

Section 115 also creates a mandatory duty, providing that whenever the Administrator receives reports giving him "reason to believe" that air emissions in the United States "cause or contribute to air pollution which may reasonably be anticipated to endanger public health or welfare in a foreign country," he "shall give formal notification thereof" to the governor of the state where the emissions originate—which would include every state and territory in the United States given the ubiquity of GHG emissions sources and the fact that the emissions mix, persist for centuries and accumulate. 42 U.S.C. §7415(a). This duty is triggered for a foreign country which EPA "determines has given the United States essentially the same rights with respect to the prevention or control of air pollution occurring in that country as is given that country by" section 115. The first element arguably has been satisfied by EPA’s endangerment finding, where the Administrator specifically found that the emissions of GHGs endangered health and welfare in foreign nations and that these impacts, in turn, endangered health and welfare in the United States.^[11] The second reciprocity prerequisite is arguably satisfied by the international commitments in the UNFCCC as defined in the Paris Agreement. Notice from the Administrator to a governor of such an international endangerment finding under section 115 is also deemed to be a finding that any state’s SIP is inadequate and specifically triggers a mandatory duty for the state to modify its SIPs to "eliminate the endangerment." The finding also arguably triggers the Clean Air Act’s "Good Neighbor Provision," id. §§ 7415(b), 7410(a)(2)(H)(ii), under which EPA has issued federal implementation plans establishing cap-and-trade programs to address interstate air pollution by conventional pollutants.^[12]  

The case for regulation of GHGs under section 115 of the Clean Air Act appears more compelling than that presented in the only other instance where section 115 has been invoked, which arose in response to the actions by Canada and downwind states to compel regulation of acid rain precursors under a 1980 memorandum of intent signed by the United States and Canada.^[13] In response to that memorandum, EPA Administrator Costle, in a letter, determined that both the endangerment and reciprocity requirements were satisfied. However, when the incoming Reagan administration refused to act further, the Costle determinations were invalidated because they were not preceded by notice and comment.¹⁴ The D.C. Circuit later upheld the Reagan administration’s rejection of a rulemaking petition by Ontario and environmental groups, based on the agency’s representation that it wished to address the endangerment, reciprocity, and SIP revisions in a single proceeding and that it did not have sufficient information to attribute emissions to individual states. Her Majesty the Queen in Right of Ontario v. EPA, 912 F.2d 1525 (D.C. Cir. 1990).^[14] In the case of GHG emissions, EPA has already made an endangerment finding including international effects, that finding has withstood judicial review, and the agency has compiled detailed information on state-by-state emissions. However, unlike the case of acid rain precursors, the specific origin of the GHG emissions is irrelevant because the emissions mix and persist in the environment, affecting the climate of the entire Earth rather than specific regions.  Thus, action might be forced by way of a citizen suit, as in NRDC v Train.  

Both mandatory requirements for economy-wide action to address greenhouse gas emissions may be triggered as long as the UNFCCC or the Paris Agreement remains in effect and can potentially be enforced by way of citizen suits. Although both may be triggered, as long as the section 115 mechanism is available, there is a substantial argument that the United States could elect to proceed under section 115 rather than by way of the NAAQS mechanism. The section 115 mechanism, particularly as applied in the Paris Agreement, would arguably provide more flexibility than the NAAQS mechanism, which can trigger deadlines. Although the less flexible aspects of the NAAQS mechanism can be avoided (for example, by only setting a secondary, welfare-based standard), the section 115 approach is not only more flexible but more consistent with addressing an international problem such as climate change. As long as withdrawal from the Paris Agreement and the UNFCCC has not become effective, or if the Paris goals are considered customary international law, that more flexible approach could still be available. Nevertheless, President Trump's announcement has put the United States in uncharted legal territory.

III.  Additional Actions by States and Cities

A large number of states and cities responded to President Trump's announcement by endorsing the Paris Agreement and announcing commitments to its goals. These states and cities have committed to undertake independent action under their own authority and to undertake litigation both to challenge federal actions to relax or eliminate federal programs and to compel federal action.  

For example, California has already implemented a program to reduce its emissions commensurate with the Paris Agreement's goal and responded to the President's announcement by reiterating its commitment to that program and to challenge federal rollbacks. California also announced its intention to cooperate with international programs. Virginia's governor ordered the development of a cap-and-trade program for the electric utility industry by the end of 2017, and most New Jersey gubernatorial candidates have committed to rejoin the Regional Greenhouse Gas Initiative (RGGI) cap-and-trade program. A number of states have announced initiatives to control methane emissions or continue reductions in transportation related emissions.

Thus, President Trump’s announcement has reinvigorated states both to develop their own climate programs and to pursue litigation to compel federal regulatory programs to create a federal regulatory floor for other states. Similar efforts resulted in programs such as California’s and RGGI, as well as the Supreme Court’s landmark decision in Massachusetts v. EPA., but had lagged after the Obama administration embraced the importance of federal leadership in addressing climate change. President Trump’s announcement, coupled with the increasingly evident impacts of climate change and worldwide recognition of the problem, may have created the perfect storm for aggressive action by the states.