Can a President Unilaterally Withdraw—and Rejoin—the UN Climate Treaty?

On Jan. 7, the Trump administration withdrew the United States from more than 60 international agreements and organizations, including the United Nations Framework Convention on Climate Change (UNFCCC). The administration justified these withdrawals by deeming the agreements “contrary to the interests of the United States” and characterized them as “anti-American, useless, and wasteful.” When the Trump administration announced the United States’s withdrawal from the UNFCCC, it revived two long-standing but unresolved constitutional questions: (a) Can a president unilaterally terminate a Senate-ratified treaty—and if so, (b) can a future president unilaterally rejoin it?

The Climate Consequences of Withdrawal

Trump’s withdrawal from these organizations marks a significant setback for international climate progress. The United States is the world’s largest historic emitter of greenhouse gases, and its exit from the UNFCCC and other climate agreements ends U.S. participation in the annual Conference of the Parties, cedes international climate leadership to China and the EU, and eliminates any U.S. influence over prospective climate rules, transparency frameworks, and adaptation finance. The U.S. withdrawal announcement has already prompted sharp criticism. The Union of Concerned Scientists, for example, released a statement calling the decision “a new low” for the Trump administration, while former Environmental Protection Agency (EPA) Administrator Gina McCarthy characterized the decision as “shortsighted, embarrassing, and foolish.” Furthermore, the U.S.’s decision to repeal the “endangerment finding” under the Clean Air Act marks another setback for climate progress. Without U.S. economic and political influence in negotiations and climate efforts on both the international and domestic fronts, the rest of the world will likely struggle to achieve meaningful climate goals.

The Law of Treaty Withdrawal

The UNFCCC was adopted by the UN in 1992 and entered into force in 1994. It functions as the cornerstone international treaty that coordinates the global response to climate change. In negotiations led by then-President George H.W. Bush, the convention sailed through the Senate with a unanimous vote in 1992—a sign of far less polarized times for climate change and environmental issues more generally. The convention established the annual Conference of the Parties—a centerpiece of international climate negotiations. Nearly every country in the world is a party to the convention, so Trump’s withdrawal—without Senate consultation—positions the U.S. as the only nation that has ever exited the convention.

The UNFCCC is legally different from, though inextricably linked to, the 2015 Paris Agreement and other follow-up agreements such as the 2023 Dubai Climate Deal that announced a global commitment to transition away from fossil fuels. The Paris Agreement and the follow-up agreements are classified as a sole executive agreement that never went through Senate advice and consent. The president has the authority to enter and withdraw from sole executive agreements without consulting Congress. In a pattern of policy reversals, President Obama signed the Paris Agreement, Trump announced the U.S. withdrawal from it in his first term, President Biden quickly rejoined, and then Trump immediately withdrew the U.S. upon taking office again. However, under U.S. constitutional law, the convention has a different status as an Article II treaty that has undergone Senate advice and consent.

Article II of the Constitution provides that the president “shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two-thirds of the Senators present concur.” But the Constitution says nothing about withdrawing from treaties, creating interpretive uncertainty over the Senate’s role (if any) to effectuate a withdrawal. While Congress has not passed follow-up legislation prohibiting presidential withdrawal from the UNFCCC, Congress has continued to appropriate funding for several UNFCCC initiatives, including billions for international climate finance initiatives. Based on historical practice, congressional acquiescence, and judicial avoidance of deciding the question of withdrawal power, the U.S. withdrawal from the convention is likely a fait accompli. As Scott Anderson astutely summarized in Foreign Affairs, most legal scholars agree that the president can exit treaties without congressional authorization as long as the withdrawal is done in “a manner consistent with international law.”

 Judicial Avoidance of the Withdrawal Question

While multiple presidents have independently withdrawn from Senate-approved treaties, the Supreme Court has declined to reach the merits of each withdrawal. For example, in 1979, President Carter withdrew the U.S. from the 1954 mutual defense treaty with Taiwan without explicit congressional approval. Sen. Barry Goldwater (R-Ariz.) challenged Carter’s decision, resulting in a case before the Supreme Court, Goldwater v. Carter. The case was dismissed on justiciability grounds, with no majority opinion establishing precedent on the underlying constitutional question.

In 2001, President George W. Bush withdrew from the Anti-Ballistic Missile Treaty over just a few congressional objections. Rep. Dennis Kucinich (D-Ohio) challenged the constitutionality of Bush’s withdrawal in Kucinich v. Bush. This lawsuit also failed on justiciability grounds, with the district court stating in a 2002 decision that the treaty termination issue is a nonjusticiable political question that “cannot be resolved by the courts.”

The executive branch clearly considers itself bestowed with the power to withdraw from treaties without Senate approval. During President Trump’s first term, the Office of Legal Counsel (OLC) issued two opinions addressing the legality of withdrawing from the Open Skies Treaty and the North American Free Trade Agreement—reaffirming that the president enjoyed unilateral withdrawal power. In the Open Skies Treaty OLC memo, the Department of Justice wrote that Congress’s attempt to place a waiting period on withdrawal “interfere[d] with the President’s exclusive authority to execute treaties and to conduct diplomacy.”

The OLC position finds support in the 2018 Restatement (Fourth) of Foreign Relations Law, Section 313, which states that the president may withdraw from treaties provided that the withdrawal is lawful under international law and there are no preexisting congressional limits on withdrawal. The 2018 Restatement reflects scholarly consensus that presidential withdrawal power exists, but the precise scope of the authority remains contested for multilateral treaties, such as the UNFCCC, that create complex and ongoing obligations to the entire international community.

Congress could attempt to block the treaty termination through legislation, but this is unlikely given today’s polarized legislature. And even if Congress did pass legislation to block withdrawal, the executive branch would likely challenge it—and it is difficult to imagine the judiciary opining on the withdrawal question, particularly with the Goldwater and Kucinich precedent.

Unilateral Withdrawal Critiques: The Mirror Image Rule

Despite the history of executive initiative and judicial avoidance, the legality of unilateral treaty withdrawal remains unsettled. Harold Koh, former State Department legal adviser, argues that “the Constitution affords the President no general unilateral power to terminate or withdraw from any international agreement, without regard to its subject matter.” Rather than an abstention from ruling on the matter, Koh regards Goldwater and Kucinich as failing to provide a solid, independent legal basis for a treaty withdrawal.

Instead, Koh proposes a “mirror image rule,” a novel but untested theory that attempts to reconcile treaty entry processes with treaty exit processes. Under Article II, to enter an international treaty, the president must obtain approval from two-thirds of the Senate. Under Koh’s proposed rule, the approval of Congress or two-thirds of the Senate would be required for treaty withdrawal, mirroring the entry process. But the judiciary has not squarely embraced the mirror rule, and it remains an untested (albeit compelling) legal theory.

Applying the Youngstown Framework

The constitutional stipulation of separated powers and checks and balances extends to foreign affairs. Justice Robert Jackson’s concurrence in Youngstown Sheet & Tube Co. v. Sawyer (1952) provides an analytical framework for categorizing presidential authority based on congressional authorization. Applying the Youngstown framework to the UNFCCC withdrawal can help to examine whether Congress agrees, disagrees, or is indifferent to this executive branch action.

The Youngstown framework establishes that presidential powers are not fixed, but instead fluctuate depending on their conjunction or disjunction with congressional powers. Over time, Congress has appropriated money to effectuate several convention initiatives, but in recent years, members have introduced legislation both supporting and opposing U.S. involvement in the convention. Meanwhile, Congress has failed to enact legislation preventing the president from withdrawing from the UNFCCC. Nor has Congress enacted legislation such as the 2019 measure requiring four months’ notice before initiating withdrawal from the Open Skies Treaty.

In the unlikely event that a court reached the merits on treaty withdrawal, the president would likely argue that current congressional inaction places the withdrawal in Justice Jackson’s “zone of twilight.” In this category, Congress and the president have concurrent authority, the distribution of power is uncertain, and congressional inertia may enable, if not invite, measures on independent presidential responsibility. In practice, treaty withdrawal lives in the zone of twilight—and has for decades.

Congress, in contrast, will try to point to the initial 1992 Senate approval as support that presidential power is at its “lowest ebb” under the Youngstown framework. The executive branch will argue the 1992 Senate resolution is historical, not a current expression of congressional will, so the lowest ebb framing doesn’t hold. When the president is at the lowest ebb category, the president can rely only on his own constitutional powers minus any constitutional powers of Congress over the matter. But without a clear, recent expression of disapproval from Congress, the lowest ebb argument faces significant legal headwinds.

In sum, the practice of unilateral withdrawal will be aided by congressional acquiescence, continued judicial deference, and reluctance to intervene. Writing in Youngstown, Jackson stated that only Congress itself can prevent power from slipping through its fingers. President Trump is withdrawing, Congress is not acting, and courts are unlikely to second-guess this decision.

How Might the U.S. Rejoin the Framework Convention

Future administrations might choose to rejoin the UNFCCC. Under international law, this process is straightforward. First, the U.S. has to join the Framework Convention before it can be a party to the Paris Agreement or other international climate agreements negotiated under the auspices of the convention. Article 23 of the convention states that a state can become a party just 90 days after it deposits its instrument of “ratification, acceptance, approval, or accession.” Article 21 of the Paris Agreement has an even shorter period—just 30 days. Depending on the results of the 2028 presidential election, there is a plausible scenario in which the U.S. is party to the Framework Convention and Paris Agreement within 120 days of the new president’s taking office in 2029.

Less examined is the constitutional question of how—and on what authority—a future president could rejoin a Senate-ratified treaty the United States has exited. Jean Galbraith outlines three potential paths for the United States to rejoin the convention under a future president: (a) receiving Senate advice and consent again; (b) rejoining through another domestic process that does not require legislative approval, such as treating the agreement as an executive agreement rather than as a treaty; or (c) treating the preexisting 1992 Senate resolution as still operative. The third option is both the most likely and legally supportable, as the original Senate resolution of advice and consent to a treaty remains in effect even after withdrawal.

The Senate’s 1992 advice and consent authorized U.S. participation in the UNFCCC; nothing in that resolution limits its authorization to a single, uninterrupted membership. Just as the president can withdraw without Senate approval (under current practice), a future president should be able to exercise the Senate’s preexisting authorization to rejoin. As Galbraith argues, a presidential administration understands itself to be bound by the specific language of existing resolutions, whether initially ratifying or subsequently rejoining the treaty.

To be sure, there are potentially complicating factors. Unilateral treaty rejoining would be blocked if Congress passes legislation that invalidates the earlier Senate resolution of advice and consent. After all, both treaties and statutes are “the supreme Law of the Land” under the Supremacy Clause. Applying the “last in time” rule, a subsequent congressional action that invalidates the 1992 Senate Resolution would bind the president.

As it stands, however, the initial resolution authorizing U.S. membership in the convention contains no text that prohibits or otherwise limits the U.S. from rejoining. Furthermore, just as courts are reluctant to reach the merits on withdrawing from treaties, the same judicial reluctance to intervene in foreign relations would apply to rejoining treaties. When a future president moves to rejoin the UNFCCC—and one hopefully will—the 1992 Senate resolution should suffice. That authorization wasn’t time-limited or conditioned on uninterrupted membership. 

What Now?

The constitutional questions surrounding treaty withdrawal and reentry remain frustratingly unresolved, yet the practical realities are not. Despite ongoing scholarly debate over the president’s unilateral withdrawal authority, historical practice, congressional acquiescence, and judicial reluctance to intervene have created a system where executive power dominates treaty termination. The same dynamic will likely govern reentry: A future president will almost certainly be able to rely on the 1992 Senate resolution to reenter the UNFCCC without seeking fresh Senate approval.

This executive dominance over treaty commitments—allowing presidents to withdraw and rejoin major international agreements at will—creates profound instability in U.S. foreign relations. The current “climate whiplash” illustrates the problem: The United States has now exited and rejoined climate agreements multiple times in just over a decade, undermining both American credibility and the international community’s ability to coordinate responses to global challenges. Allies and adversaries alike cannot rely on U.S. commitments that may evaporate with each change of administration—and when America steps back, others step forward. China is the most likely candidate to fill the leadership void.

Congress bears significant responsibility for this state of affairs. The Constitution’s silence on treaty withdrawal has created a vacuum that the executive branch has eagerly filled. If Congress believes Senate approval should be required for withdrawal—mirroring the entry process—it must pass legislation saying so. If Congress believes existing Senate resolutions should expire upon withdrawal, it must invalidate them. Congressional inaction is itself a decision, and one that cedes foreign policy control to the presidency.

The immediate consequences of withdrawal from the UNFCCC are severe. Though official withdrawal will not take effect for one year after notification, the United States—the world’s largest historical emitter of greenhouse gases—will have the dubious honor of becoming the only nation ever to exit the treaty that underpins global climate action. As a non-party, the United States will forfeit its voting rights and formal influence at the annual Conference of the Parties, leaving the field to China and other major powers to shape climate policy without American input. The United States will have gone from climate leader to bystander.

In the interim, the burden falls on subnational actors—states, cities, businesses, and civil society—to sustain climate progress without federal support. Many states have already committed to maintaining Paris Agreement targets regardless of federal policy, and these efforts must intensify. The economic opportunities in clean energy and the physical realities of climate change will not wait for constitutional clarity or political stability in Washington.

The Trump administration's withdrawal from the UNFCCC crystallizes a fundamental question about American governance: Should the president possess unchecked power to terminate treaty obligations that the Senate approved and that create duties to the entire international community? Until Congress asserts itself or the courts overcome their reluctance to decide these questions, the answer will remain yes—with all the diplomatic chaos and climate consequences that follow. Future administrations may reverse this withdrawal. But the damage to American credibility and global climate cooperation may prove far more difficult to repair.