Trump has just won the elections. Can he somehow stop the US from participating in the UN COP21 climate change agreement (which was already signed formally by the US)?

Also I've read here that

To take effect, the Paris Agreement needs formal ratification by 55 countries that account for 55 percent of global emissions.

If the US can still bail out, would it also be possible that these critical thresholds are not reached?

3 Answers 3


No, Trump cannot undo the UN climate change agreement. All he can do is isolate the USA from participating in it.

The USA signed the Paris Agreement on 22 April 2016, and became a formal Party to it on 3 September 2016. John Kerry and his team put a lot of work into word-smithing it to ensure it could be agreed by the US president, without the Senate.

It has now passed the two hurdles of at least 55 countries, and countries that represent at least 55% of global emissions, so it has already formally entered into force, as of earlier this month (Nov 2016). At time of writing, it had 103 parties representing 73.38% of global emissions; without the USA, this would be 102 parties representing 55.49% of global emissions, so still exceeding the twin hurdles which were needed for it to enter into force in the first place.

Trump, when president, could withdraw the USA's commitment to the Paris Agreement. However, the Agreement has already entered into force internationally, and all the remaining participants will continue to implement it. So Trump cannot undo the Paris Agreement. All he can do is isolate the USA from participating in it.

Note that the 55-country, 55%-emissions thresholds are not ongoing criteria; instead, they are thresholds that need to be met once for the Paris Agreement to enter into force (article 21 para 1, pdf p49):

This Agreement shall enter into force on the thirtieth day after the date on which at least 55 Parties to the Convention accounting in total for at least an estimated 55 per cent of the total global greenhouse gas emissions have deposited their instruments of ratification, acceptance, approval or accession.

That has already happened, so there is no further legal significance attached to those thresholds.

Article 28 (pdf p51, ibid) deals with Parties withdrawing from the agreement:

  1. At any time after three years from the date on which this Agreement has entered into force for a Party, that Party may withdraw from this Agreement by giving written notification to the Depositary.
  2. Any such withdrawal shall take effect upon expiry of one year from the date of receipt by the Depositary of the notification of withdrawal, or on such later date as may be specified in the notification of withdrawal.
  3. Any Party that withdraws from the Convention shall be considered as also having withdrawn from this Agreement.
  • 10
    Many, many problems with this answer. The USA wouldn't be isolated. There is no reason to believe so. The answer doesn't even try to address. The USA didn't sign it, Barack Obama's administration did. It was not presented to the Senate, much less voted on, so it has no force in America. And it's extremely doubtful that once the US pulls out all other country would remain in it. Calls for a future conclusion
    – user9790
    Commented Nov 9, 2016 at 16:40
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    I think you need to address if Trump can indirectly undo the Paris Agreement if he starts the first in a series of countries reneging the Agreement (e.g. what if China and India withdraw)
    – Nick T
    Commented Nov 9, 2016 at 17:07
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    @NickT I've edited the answer to cover what the Agreement says about withdrawal. I suspect that this doesn't directly address what you ask, but it's the best I could do without speculating about a myriad of possible futures.
    – 410 gone
    Commented Nov 9, 2016 at 17:31
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    @NickT the first negotiations by the Parties on the specifics of implementation (CMA1) are starting now in tandem with COP22, in Marrakech. Once those are done, we'll start to get an idea of the direction that's taking; further clarity may take a few years. After that, one possible route to recourse will be via trade sanctions: as those sanctions were backed by a UN treaty, the WTO wouldn't have much to say against them.
    – 410 gone
    Commented Nov 9, 2016 at 17:41
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    To take this even further, there are no enforcement mechanisms in the treaty. So the idea that it even will be followed is laughable.
    – user9790
    Commented Nov 9, 2016 at 20:56

Trump has just won the elections. Can he somehow stop the US from participating in the UN COP21 climate change agreement (which was already signed formally by the US)?


In order to be binding in the United States (US), a treaty must be ratified by two thirds of the Senate (67 Senators). UN COP21 was not. It was just signed by Barack Obama.

It is conceivable that the Senate could approve a request for ratification from Obama before Trump takes office. However, they do not have enough votes in favor to do that in either the current or the 2017 Senate. Once Trump takes office, he can withdraw any ratification request that Obama may have sent. And then Trump is free not to participate in the agreement.

Absent action by the Senate in the remainder of Obama's term, Trump will control any ratification activity in his term. The Senate can't approve a ratification request unless he sends it. The treaty has no legal impact on the US unless it is ratified.

Of course, Trump has no ability to tell any other country what to do. So every other country is welcome to continue following it even if the US does not. Whether or not they count any additional criteria as being met would also be up to interpretations outside the US.

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    If I understand your answer correctly, it is actually "No, it's up to the Senate"?
    – user5097
    Commented Nov 9, 2016 at 9:58
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    No. The Senate has not ratified the treaty and will not do so. They are nowhere close to having the votes to approve a ratification. That would require 67 votes and they are closer to 50. It is conceivable that the Senate could approve ratification before Trump takes office, but it is extremely unlikely. And they certainly haven't done so yet. So the current state is that Trump could just ignore the agreement.
    – Brythan
    Commented Nov 9, 2016 at 10:03
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    Thanks for you answer. I've read here that "To take effect, the Paris Agreement needs formal ratification by 55 countries that account for 55 percent of global emissions." So if the US bails out, it is very well possible the agreement won't reach the critical threshold.
    – THelper
    Commented Nov 9, 2016 at 11:21
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    I really feel this answer is misleading. It says yes, but also says it's not binding on us anyway and that it isn't even his actions, but the senates, that would make it happen.
    – corsiKa
    Commented Nov 9, 2016 at 15:34
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    @corsiKa The original question was if Trump is free. Trump is. The Senate has not taken the action that would make him unfree. They are not going to take the action that would make him unfree. He is free. Once in office, they can't make him unfree without action from him.
    – Brythan
    Commented Nov 9, 2016 at 19:50

Yes, and a qualified no. International law and domestic policy are separate. And complicated.

According to the UN Treaty Database, Obama signed the Paris Agreement on April 22, 2016 and accepted it on September 9, 2016. These words have specific legal meaning.

Signatures are subject to ratification, acceptance, or approval. Obama's signature signaled the US intention to comply with Paris Agreement once in effect, but not obliging the US to do so until formally ratified, accepted, or approved by its own domestic process.

Obama then sends an acceptance letter. What is this? And how is it different than ratification or approval? Let's define the terms first:

  • Ratification

    ... a state indicates its consent to be bound to a treaty if the parties intended to show their consent by such an act.... The institution of ratification grants states the necessary time-frame to seek the required approval for the treaty on the domestic level and to enact the necessary legislation to give domestic effect to that treaty.

  • Acceptance

    The instruments of "acceptance" or "approval" of a treaty have the same legal effect as ratification and consequently express the consent of a state to be bound by a treaty. In the practice of certain states acceptance and approval have been used instead of ratification when, at a national level, constitutional law does not require the treaty to be ratified by the head of state.

But wait, Article II section 2 says the President can sign treaties only with the "advice and consent" of the Congress:

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

This is a treaty, and the US Constitution says the President requires advise and consent, so how could Obama just sign it?

Turn now to the Center for Biological Diversity Climate Law Institute, which drafted a 2009 working paper titled "Yes, He Can: President Obama’s Power to Make an International Climate Commitment Without Waiting for Congress". In this working paper, CBD identified a two prong legal footing on which Obama could sign, apparently without domestic ratification, the Paris Agreement:

  1. The Clean Air Act, as amended, of 1990, which provides that

    the President may enter international agreements... and develop standards and regulations which protect the stratosphere consistent with regulations applicable within the United States."

  2. The Global Climate Protection Act of 1987, which provides that the President may "identify technologies and activities to limit mankind's adverse effect on the global climate" by "slowing the rate of increase of concentrations of greenhouse gases in the atmosphere in the near term" and "developing and proposing to Congress a coordinated national policy on global climate change." This legislation also states that the "Secretary of State shall be responsible to coordinate those aspects of United States policy requiring action through the channels of multilateral diplomacy, including the United Nations Environment Program and other international organizations."

So, Obama accepted the Paris Agreement on the good faith basis that he had already had the domestic authority to commit the US to international accords. That acceptance is legally binding under international law.

Beside upholding the obligation, the US could ignore, denounce, or withdraw from it. The last two have specific, legal meaning, but all three boil down to the same thing: nothing happens. Unfortunately, the Paris Agreement has no teeth, no provisions for punishing those who agree to uphold but ultimately don't uphold. In this regard, Paris is more like a recommendation than a contract.

So, yes Trump could have the Secretary of State draft a notice of denunciation, inter alia, and send it to the UN, effectively signaling the end of US international cooperation. But, no, short of legislation change, he can't really stop the US paricipating in the essence of the Paris Agreement: the Clean Air Act and Global Climate Protection Act proxy the agreement's fundamental environmental and economic aspects.

To answer your last question, the Paris Agreement went into effect in November. Even if the US defaulted, the treaty would continue to be in force, per Vienna Convention on the Law of Treaties, as amended

  • 8
    Nice answer, welcome to the site.
    – SJuan76
    Commented Nov 9, 2016 at 22:08
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    The Constitution specifically specifies that treaties cannot be ratified without approval from the Senate. While the President may have the authority to enter into agreements with regard how his administration will exercise powers given to it by Congress, I don't see how any such agreements could be construed as "formal ratification".
    – supercat
    Commented Nov 9, 2016 at 23:53
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    Your Quote of the Clean Air Act omits a rather pertinent portion. Further, the president is only authorized to enter into negotiations to develop standards. That does not extend to applying or enforcing standards. Commented Mar 22, 2017 at 14:56

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