On November 4, 2019, the Trump administration notified the United Nations that the United States was withdrawing from the Paris Agreement, prompting expressions of regret from a number of countries. Although President Trump had announced in June 2017 that the United States intended to withdraw from the Paris Agreement, its terms had prevented the United States from giving formal notice of withdrawal until November 4, 2019. The withdrawal will take effect on November 4, 2020. Domestically, the governors of many U.S. states responded to the withdrawal by reaffirming their commitment to the goals of the Paris Agreement, consistent with recurring tensions between the Trump administration and progressive states with respect to climate. In another major manifestation of these tensions, on October 23, 2019, the United States sued California over the state's cap-and-trade agreement with Quebec, Canada, alleging that this agreement is an unconstitutional exercise of foreign affairs powers.

Opened for signature in April of 2016, the Paris Agreement seeks to maintain the global average temperature “well below 2°C above pre-industrial levels and pursu[e] efforts to limit the temperature increase to 1.5°C above pre-industrial levels.”Footnote ¹ Each state party is required to “prepare, communicate and maintain successive nationally determined contributions [NDCs] that it intends to achieve.”Footnote ² Additionally, under the Paris Agreement, “[d]eveloped country Parties shall provide financial resources to assist developing country Parties with respect to both mitigation and adaptation in continuation of their existing obligations under the [United Nations Framework Convention on Climate Change].”Footnote ³ The Paris Agreement entered into force on November 4, 2016, thirty days after fifty-five nations became party to it.Footnote ⁴ Currently, there are 187 parties to the Paris Agreement.Footnote ⁵

The United States signed the Paris Agreement on April 22, 2016,Footnote ⁶ and deposited its instrument of acceptance on September 3, 2016.Footnote ⁷ In having the United States join the Paris Agreement, the Obama administration acted without seeking or receiving specific congressional authorization to do so, concluding that the executive branch had the domestic authority to make this commitment on behalf of the United States.Footnote ⁸ In its 2016 NDC, the United States pledged to “reduc[e] its greenhouse gas emissions by 26–28 per cent below its 2005 level in 2025 and to make best efforts to reduce its emissions by 28%.”Footnote ⁹

In June 2017, Trump announced that “the United States [would] withdraw from the Paris climate accord . . . but begin negotiations to reenter either the Paris accord or an . . . entirely new transaction on terms that are fair to the United States, its businesses, its workers, its people, its taxpayers.”Footnote ¹⁰ He stated that the United States was “ceas[ing] all implementation of the nonbinding Paris accord and the draconian financial and economic burdens the agreement imposes on our country.”Footnote ¹¹ Since Article 28(1) of the Paris Agreement prevents parties from giving formal notice of withdrawal until three years after the Agreement's entry into force, the earliest possible date for such notice was November 4, 2019.Footnote ¹²

On November 4, 2019, the United States formally notified the United Nations that it would be withdrawing from the Paris Agreement.Footnote ¹³ Secretary of State Michael Pompeo explained that the United States was withdrawing

Consistent with the terms of the Paris Agreement, the withdrawal will take effect on November 4, 2020, one year after the date of notice of withdrawal.Footnote ¹⁵ As a matter of international law, the United States could rejoin the Paris Agreement at any point thereafter, following a thirty-day waiting period.Footnote ¹⁶ The United States remains a party to the United Nations Framework Convention on Climate Change.Footnote ¹⁷

The U.S. notification of withdrawal was met with international regret. China and France issued a joint declaration “reaffirm[ing] their strong support for the Paris Agreement, which they consider an irreversible process and a compass for strong action on the climate,”Footnote ¹⁸ and some other countries similarly emphasized their continued commitment to the Paris Agreement.Footnote ¹⁹ Likewise, the European Commission reiterated that the Paris Agreement “is here to stay, its door remains open and we hope the U.S. will decide to pass it again one day.”Footnote ²⁰ The spokesperson for the United Nations secretary-general stated that “our determination to move forward on the implementation of the Paris Agreement remains unchanged” and “encourage[d] member states to actively engage . . . to raise ambition, to tackle and defeat climate change.”Footnote ²¹

Domestically, the U.S. notification of withdrawal highlighted the strong divergence between the U.S. government and numerous subnational governments with respect to the issue of climate. Immediately after the U.S. notification, a bipartisan coalition of twenty-five state governors “reaffirm[ed] our commitment to supporting climate action and . . . strongly oppos[ed] the Administration's decision to formally withdraw from the Paris Agreement.”Footnote ²² They noted that since June 2017, “our states have adopted or strengthened 29 greenhouse gas reduction targets and ramped up zero-carbon power generation, with 19 states now enacting or pursuing goals for 100 percent carbon-free or clean power by 2030 or later.”Footnote ²³ In this same time period, a sizeable number of states and major cities have challenged the Trump administration's domestic climate actions, including by filing lawsuits contesting its rollback of the Clean Power PlanFootnote ²⁴ and energy-efficiency standards.Footnote ²⁵

California has been a leader in these subnational attempts to address climate change and has consequently itself faced resistance from the Trump administration. In September 2019, the Trump administration revoked California's authority to set stricter vehicle emissions standards than those established under federal law,Footnote ²⁶ leading California—along with twenty-two other states, the District of Columbia, and two cities—to sue the administration over this revocation.Footnote ²⁷ In the latest salvo, on October 23, 2019, the United States filed a lawsuit against California, alleging that the cap-and-trade agreement between California and Quebec, Canada, is unconstitutional.Footnote ²⁸ This agreement “link[s]” California and Quebec's pre-existing cap-and-trade programsFootnote ²⁹ by allowing regulated entities in California and Quebec to trade their emissions allowances with each other.Footnote ³⁰ In challenging this agreement, the United States alleges that it is “an independent foreign policy in the area of greenhouse gas regulation” which “intrude[s] into the federal sphere,” “complexif[ying] and burden[ing] the United States’ task . . . of negotiating competitive international agreements.”Footnote ³¹ In response, the governor of California described this lawsuit as a “political vendetta against California, our climate policies and the health of our communities,” adding that “the Trump administration's abysmal record of denying climate change and propping up big polluters makes cross-border collaboration all the more necessary.”Footnote ³² The case is pending before a federal district judge in the Eastern District of California.Footnote ³³