On Wednesday, 7th January 2026, the President of the United States, Donald Trump, published a Presidential Memorandum directing the withdrawal of the United States from 66 international organisations, including, among them, the International Panel on Climate Change (IPCC) and the United Nations Framework Convention on Climate Change (UNFCCC).
Signed by the US in June 1992 and ratified in October of that same year, the UNFCCC has served as the cornerstone of international climate governance for more than three decades. Against this backdrop, President Trump’s announcement of a US withdrawal from the Convention is of particular significance. While the United States has previously withdrawn from, rejoined, and again announced its withdrawal from the Paris Agreement, withdrawal from the UNFCCC itself entails far more profound legal and political consequences, given its status as the parent framework of the international climate regime and its near-universal ratification by the international community. This unprecedented development under the UNFCCC, therefore, raises fundamental legal questions, most notably whether withdrawal from the Convention through President Trump’s Presidential Memorandum is legally permissible, and, if so, whether and under what conditions a withdrawing Party may subsequently rejoin.
Understanding President Trump’s Presidential Memorandum
It is first interesting to look into what the Presidential Memorandum published on Wednesday, 7th January 2026, entails in practice. Of note is its particular definition of ‘withdrawal’: “For United Nations entities, withdrawal means ceasing participation in or funding to those entities to the extent permitted by law”. Whilst the intention to withdraw is clear, this definition leaves some room for interpretation and a wide margin to the decision-maker on how to take this forward. It could entail a formal withdrawal by notifying the UNFCCC, but it does not necessarily entail that the US formally withdraws; it simply entails ceasing participation and funding. It is unclear at this stage how the administration intends to put into practice this Memorandum, both options seem to be reasonable possibilities. Therefore, it remains interesting to explore the legal context of the potential withdrawal.
Legal authority of a Party to withdraw from the UNFCCC under international law
Under Art. 25(1) of the UNFCCC, “At any time after three years from the date on which the Convention has entered into force for a Party, that Party may withdraw from the Convention by giving written notification to the Depositary.” According to Art. 25(2) that withdrawal will take effect one year after the notification, and finally, according to Art. 25(3) of the Convention, withdrawal from the Convention shall also be considered as withdrawal from any protocol.
Therefore, as a matter of international law, any Party to the UNFCCC may withdraw so long as it does so three years after the date on which it entered into force for that Party. As the UNFCCC entered into force in the US in October 1992, over thirty years ago, the US can withdraw from the UNFCCC under international law. However, under domestic law, the question arises as to whether the President has the authority to withdraw the US without an act of Congress.
President Trump’s uncertain legal authority to unilaterally withdraw from the UNFCCC
Art. II Section 2 Clause 2 of the US Constitution establishes the relevant legal authority of the President to make treaties “He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur;”. Therefore, to become a Party to a treaty, the US President requires the advice and consent of the Senate, which was obtained prior to signing the UNFCCC in 1992. The Constitution is, however, silent on the question of withdrawal.
One expansive view is that the US Supreme Court addressed this question indirectly in United States v. Curtiss-Wright Export Corporation et al. (1936). In that case, the Court recognised the President as the sole organ of the Federal government in the field of international relations, thereby granting them wide powers to act – i.e. to withdraw from a treaty – without the need for an act of Congress. Thus, the president may unilaterally decide on behalf of the country to terminate a treaty “that no longer serves the national interest.”[1] However, the decision concerned Congress’s delegation of power to the President, rather than the President’s authority to terminate treaties, which the Court has never explicitly addressed. Under this expansive understanding of the Court’s reasoning, where the Senate has not indicated that withdrawal from the treaty requires prior approval, the President could be understood to possess the legal authority to withdraw the United States from the treaty.
Nevertheless, views on this differ, and it could also be argued, by applying a ‘mirror principle’ to the Constitution’s consent and advice clause,[2] that, as the consent and advice of the Senate were necessary to enter into the Convention, the consent and advice of the Senate are also necessary to withdraw from the Convention, meaning that President Trump’s Memorandum (and in particular its direction to executive agencies to withdraw) is inoperative until the Senate votes on this matter. The President’s unilateral withdrawal could also be challenged if it were established that it infringes on an existing congressional power, or if it were proved that by withdrawing from the UNFCCC, this, in practice, implied the power to enter into a new treaty.
Accordingly, under international law, there is nothing that would prohibit the US’s withdrawal from the UNFCCC. However, under domestic constitutional law, the President’s unilateral power to withdraw the United States from the UNFCCC remains unestablished and uncertain. As such, it is likely that this decision will be challenged, but highly unlikely that the administration will await a legal determination of this matter. In practical terms, it is safe to assume that the United States will no longer be involved in the UNFCCC process, whether the withdrawal is formal or not.
Legal authority to rejoin the UNFCCC and the Paris Agreement
While the Biden administration was able to swiftly rejoin the Paris Agreement through an executive order at the end of the Trump administration, formal withdrawal from the UNFCCC fundamentally complicates that process and limits future administrations’ ability to rejoin the Paris Agreement.
Art. 20(1) of the Paris Agreement provides that only Parties to the UNFCCC may sign and ratify the Agreement. Therefore, withdrawal from the Convention prevents any future administration from rejoining the Paris Agreement unless and until the United States first accedes to the UNFCCC. This is significantly more complex than on previous occasions of the US re-entering a convention. The Biden administration’s re-entry into the Paris Agreement did not require Senate advice and consent, as the Paris Agreement had not been adopted via the power under Article II, § 2 of the Constitution. Rather, at the time of adoption and re-adoption, the administration relied on existing executive authority. Similarly, although the US previously withdrew and then rejoined UNESCO, that process also rested on a different legal basis to Art. II Section 2 of the US Constitution.
Had President Trump not also withdrawn the US from the UNFCCC, the straightforward process would have remained open to future administrations to re-enter the Paris Agreement. However, once the United States ceases to be a Party to the Convention, the question becomes, first and foremost, how to rejoin the UNFCCC. Although rather straightforward under international law, with no elements of the Convention that prohibit a Party from rejoining, it does raise unresolved constitutional and procedural questions at the domestic level. In particular, it remains unclear whether and how a President could re-accede to a Convention that was originally ratified with the advice and consent of the Senate.
In light of both the current and the historical political landscape, obtaining the advice and consent of the Senate for any international convention that is even mildly controversial is seen as challenging, given the 2/3 majority requirement. Therefore, as some legal scholars have pointed out, having to obtain the advice and consent of the Senate in future to re-accede to the UNFCCC will inevitably limit a future administration’s power on this matter.[3]
Within this unsettled landscape, Jean Galbraith has argued that it would be possible, in most circumstances, for a President to rejoin a Convention that was ratified following the advice and consent of the Senate, and that a previous President withdrew from, without having to obtain new advice and consent of the Senate.[4] She explains that the Senate’s resolution of consent and advice remains operative, notwithstanding long lapses between the resolution and ratification, and the de-establishment and re-establishment of treaty relations are common occurrences in multilateral treaties, which do not require the Senate to repeatedly intervene. In essence, while the President enjoys broad authority in the conduct of international relations, that authority does not extend to resetting the treaty-making process to its constitutional starting point.
However, this remains an open question. One may argue that due to art. 25(2) of the UNFCCC, which provides for a three-year commitment, the act of rejoining the UNFCCC would not simply be a return to the status quo. This would be a return to different legal circumstances to those that the US would have been under prior to withdrawing, which would imply obtaining a new resolution of advice and consent. Further, if one were to prove that material changes had been made to the UNFCCC since the Senate gave its resolution of advice and consent in 1992, that resolution would not apply to the substantially different treaty version that is currently in place. Nevertheless, this would be challenging to establish as the core treaty text has not been amended; rather, there have been additional protocols adopted, amendments to its annexes, and a whole host of COP decisions which have operationalised the implementation of the Convention.
In conclusion, this Presidential Memorandum has given rise to many questions. Aside from a clear signal of an intention to withdraw from, amongst others, the UNFCCC, it is still unclear what ‘withdrawal’ from the UNFCCC will look like for the US. It is also unclear whether the President possesses the authority under US constitutional law to order the withdrawal from the UNFCCC without renewed Senate involvement, and this decision will likely be challenged in Court.
From a practical perspective, the US’s absence from the negotiations has already been particularly noticeable, as one of the lead negotiating actors, leaving a wide gap to be filled and impacting commitments on climate finance for years to come. It will also require stronger commitments from other countries to compensate for the US’s lack of progress on climate commitments, ensuring the UNFCCC secretariat’s budget continues to grow in line with growing mandates, despite the fact that the US was supposed to contribute to around 21% of the 2026-2027 budget.[5] Notably, it remains to be seen to what extent others will be willing to step in, or whether the withdrawal might embolden them to follow suit and/or seek to dilute their commitments further.
Withdrawal from the Convention alters the legal landscape for future administrations and, in the absence of clear precedent, it remains uncertain whether a future President could rejoin the UNFCCC, and ultimately the Paris Agreement, without renewed advice and consent of the Senate. In practice, the United States could still participate in the UNFCCC indirectly, as an observer, including through state and civil society participation. However, this decision will inevitably reduce the impact the United States has on international climate change governance.