States and Cities As 'Norm Sustainers': A Role for Subnational Actors in the Paris Agreement on Climate Change

52 Pages Posted: 11 Jan 2019 Last revised: 13 Feb 2019

Date Written: 2019


President Donald Trump’s declared intent to withdraw the United States from the Paris Agreement on climate change has prompted many states and cities in the United States to redouble their efforts on climate change and to pledge support for the international treaty. U.S. subnational states and cities cannot be parties to the Paris Agreement, so what do their declarations of support mean from the perspective of international law? Using Harold Koh’s theory of transnational legal process as a framework, I address this question by integrating the literature on international climate law and state and the scholarship on local climate innovation. I argue that subnational actors are “norm sustainers” who can help to ensure the success of the Paris Agreement even if the U.S. withdraws from the treaty.

When subnational actors pledge to uphold a global treaty, like the Paris Agreement on climate change, they act as norm sustainers and contribute to the transnational legal process in three distinct ways. First, by publicly benchmarking their own progress on the U.S. targets under the Paris Agreement, subnational norm sustainers can signal to other nation-states that a significant portion of the United States is still committed to the goals of the Paris Agreement. Consistent with the treaty’s emphasis on transparency for compliance, such subnational disclosure could encourage other countries to achieve their own national targets, or, at the very least, help to prevent a decrease in ambition in the wake of a U.S. withdrawal from the treaty.

Second, states and cities can sustain and strengthen key norms of international environmental law that are embedded within the Paris Agreement. For example, President Trump has essentially repudiated the principle of common but differentiated responsibilities and respective capabilities. I argue that states and cities give this principle meaning when they tie their own climate policies to the Paris Agreement.

Finally, as norm sustainers, states and cities can demonstrate the feasibility of climate actions in a way that lays the groundwork for national policy, as the literature on cooperative federalism in the United States has long recognized. Thus, even if President Trump fulfills his campaign promise of withdrawing the United States from the Paris Agreement on climate change, the sustaining efforts of states and cities could enable a future president to rejoin the treaty.

President Trump’s actions threaten to derail global progress on climate change by encouraging other countries to defect from the Paris Agreement. Although U.S. states and cities cannot be parties to the treaty, their actions as norm sustainers can help to ensure the treaty’s success and heighten international ambition on climate change.

Keywords: climate change, Paris Agreement, states, cities, subnational, transnational legal process, international environmental law

Suggested Citation

Murthy, Sharmila, States and Cities As 'Norm Sustainers': A Role for Subnational Actors in the Paris Agreement on Climate Change (2019). Virginia Environmental Law Journal, 2019; Suffolk University Law School Research Paper No. 19-6. Available at SSRN: or

Sharmila Murthy (Contact Author)

Suffolk University Law School ( email )

120 Tremont Street
Boston, MA 02108-4977
United States

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