In an interview with the New York Times, on November 22, 2016, Donald Trump said he had an "open mind" over US involvement in the Paris Agreement. During his electoral campaign he had proclaimed that he intended to "cancel' this Agreement. The international community meeting in Marrakech for the COP 22 has shown concern over this position as the United States is responsible for about 18 percent of global greenhouse gas emissions and its withdrawal from the Paris Agreement could threaten the goal of limiting the global temperature rise to below 2°C.

We can still hope that the President-elect will not pursue this election promise. No doubt he might technically pull the United States out of the Paris Agreement, but in doing so the future Trump administration would be taking both a diplomatic and a legal risk.

A withdrawal from the Paris Agreement would be permissible within a four-year period

From a procedural point of view, if the American government cannot cancel the Paris Agreement on behalf of all signatory States, it can still withdraw from the Agreement. There are two ways the U.S. government could do this. First, the Paris agreement allows States to withdraw, but only after a certain period of time. In accordance with Article 28, withdrawal is permissible only from the third year following the entry into force of the Agreement, which means not until November 2019. In addition, the withdrawal will not take effect before one year from that date. Therefore, at the earliest, the U.S. withdrawal will be effective in November 2020, by the end of Donald Trump's term.

Second, though more radical, the U.S. could withdraw from another agreement: the United Nations Framework Convention on Climate Change (UNFCCC) (the "Framework Convention"), negotiated at the Earth Summit in Rio de Janeiro in 1992. The withdrawal from the Framework Convention would lead ipso facto to the withdrawal from the Paris Agreement. Should this happen, the withdrawal will take effect within a shorter time period of one year.

Alternatively, and more simply, the future Trump administration could simply disregard its commitments under the Paris Agreement. The United States Intended Nationally Determined Contribution aims at reducing its greenhouse gas emissions from 26 percent to 28 percent of their 2005 level by 2025, but the Paris Agreement does not include any sanction in case these objectives are not met. The United States could therefore disregard its commitments with impunity.

U.S. withdrawal from the Paris Agreement would pose two major risks. The first one is diplomatic in nature. The diplomatic risk: U.S. isolation

Some fear the so-called "domino effect" whereby some States, taking notice of the U.S. withdrawal, could also decide to disregard their climate commitments. This scenario cannot be entirely excluded.

However, it is more likely that a U.S. withdrawal from the Paris Agreement could backfire, leaving the U.S. isolated on the diplomatic stage as a result. As the COP 22 put into light, the global consensus that emerged from Paris to deal with climate change collectively has been consolidated in Marrakech. Should the United States withdraw, it will assume the risk of being out of this common path, leaving the field open to challengers. China, determined to move forward with climate change, and the European Union could take the lead on developing low-carbon economies.

The legal risk: climate liability of the U.S.

It is clear that global warming will result in damages, and a key question is who will bear these costs. The Governor of the Bank of England, Mark Carney, gave a speech on September 29, 2015 at Lloyd's of London. He explained that because of the rapid sea level rise, the number of weather-related loss events has tripled since the 1980s. He showed concern on liability risks and asked what would happen "if parties who have suffered loss or damage from the effects of climate change seek compensation from those they hold responsible"?

Should the United States withdraw from the Paris Agreement, victims of global warming could initiate lawsuits against the federal government. These actions could be brought in American courts, or even domestic courts of other countries who have suffered damage. The courts could hold that the Unites States' decision to withdraw from, or to not implement, the Paris Agreement has caused damage and the victims should be fully compensated.

One thing is certain: in France, such a withdrawal would be unconstitutional. It would be contrary to Article 10 of the Environment Charter, which states that "France's actions at both European and international levels" are to draw inspiration from the objectives of environmental protection. In addition, repealing regulations such as the Clean Power Plan would likely be contrary to the principle of "non-regression", a principle provided by law. Finally, it will be at odds with French administrative case law: in a ruling of March 3, 2004, the highest administrative court (the "Conseil d'Etat") held the French State liable for negligence due to its failure to take positive action to protect workers' health when the risks associated with asbestos exposure at work were clearly demonstrated by scientific studies.

These legal principles could inspire the American courts. Indeed, a decision of the Oregon District Court took the first step towards this on November 10, 2016. The case concerned a group of 21 children and teenagers of Our Children's Trust who filed a lawsuit against the federal government in August 2015. They claimed that the government's inaction with regards to climate change violated both (i) their constitutional right to life, freedom and property (Due Process Clause) and (ii) the Public Trust doctrine whereby the State holds its natural resources in trust for its citizens. The Court denied the government's motion to dismiss the case. A chance: the mobilization of American civil society in favor of the climate

Paradoxically, compliance with U.S. climate commitments could be the result of the actions of civil society rather than of the federal government.

In the U.S., local and regional actors have been involved in the development of clean energies for a long time. Further, almost 400 American companies have called on their representatives "to pursue the participation of the U.S. in the Paris agreement."

This mobilization gives us cause for optimism: no matter the reluctance of Trump's administration to take further action to reduce greenhouse gas emissions, the civil society is already moving forward. This is in line with the report of the Environment Committee of the Club des Juristes on the growing role of non-state actors on the international stage ("Increasing the Effectiveness of International Environmental Law", available at http://www.leclubdesjuristes.com/report-increasing-the-effectiveness-of-international-environmental-law-duties-of-states-rights-of-individuals/). Now more than ever, the protection of the environment is a common concern to all citizens.