The traditional boundaries of international relations are undergoing a significant shift as subnational entities—states, provinces, and major metropolitan hubs—increasingly bypass national governments to forge their own global alliances. This phenomenon, often termed "paradiplomacy," has moved to the forefront of the global climate agenda, creating a complex web of cooperation that persists even when national leaders remain at odds. Most recently, this trend was highlighted by a high-profile climate and energy agreement between the State of California and the United Kingdom’s Labour government, an arrangement that has reignited a fierce debate over the constitutional limits of state-level foreign policy and the future of the global energy transition.
The memorandum of understanding (MOU) signed by California Governor Gavin Newsom and representatives of the British government aims to accelerate decarbonization efforts, bolster climate resilience, and facilitate the exchange of technical expertise. The agreement focuses on mutually beneficial economic and innovation activities, specifically targeting research and academic cooperation in the clean energy sector. While such agreements are framed as technical and economic partnerships, they carry immense political weight, signaling to the international community that large segments of the American economy remain committed to the goals of the Paris Agreement, regardless of the prevailing winds in Washington D.C.
The Friction Between Federal and Subnational Authority
The reaction from the White House was swift and critical. President Donald Trump, currently in his second term, characterized the deal as "inappropriate," asserting that the United Kingdom should not be engaging in climate-focused diplomacy with a state governor. The administration’s stance is rooted in a strict interpretation of federalism, which posits that the executive branch holds the exclusive mandate to conduct foreign affairs. This tension is not merely rhetorical; it reflects a fundamental divergence in policy. While California and its allies push for an aggressive transition to renewables, the federal government has pivoted toward a "fossil fuel first" strategy, characterized by the cancellation of clean-energy subsidies, the reduction of regulatory oversight by the Environmental Protection Agency (EPA), and renewed support for the coal and offshore drilling industries.
This clash is a continuation of a legal and political battle that began during Trump’s first term. In 2019, the Department of Justice filed a lawsuit to dismantle the California-Quebec cap-and-trade market, arguing that the agreement violated the U.S. Constitution’s Treaty and Compact Clauses. These clauses generally prohibit states from entering into treaties or compacts with foreign powers without the consent of Congress. However, the litigation was dropped by the Biden administration in 2021, and in 2022, President Biden signed legislation that formally recognized the importance of subnational diplomacy. That era also saw the creation of a dedicated division within the State Department to coordinate with cities and states. Under the current administration, these institutional supports have been largely dismantled, forcing states back into a defensive and independent posture.
A Chronology of Subnational Climate Action
The evolution of subnational climate diplomacy has been marked by several key milestones over the past two decades:
- 2005: The Formation of C40 Cities. Initially a group of 18 megacities, the C40 has grown into a network of 97 global cities representing one-twelfth of the world’s population and a quarter of the global economy. The group focuses on urban-scale solutions to emissions and sustainable infrastructure.
- 2014: The California-Quebec Linkage. California and the Canadian province of Quebec officially linked their cap-and-trade programs, creating one of the largest carbon markets in the world. This serves as a primary example of how regional governments can synchronize economic policy across national borders.
- 2017: The Launch of the U.S. Climate Alliance. In response to the federal government’s initial withdrawal from the Paris Agreement, a bipartisan coalition of governors formed this alliance to uphold the treaty’s goals at the state level. Today, it includes over 20 states representing a significant portion of the U.S. GDP.
- 2022: Formalization of Subnational Diplomacy. The Biden administration’s introduction of a "special representative for city and state diplomacy" marked the first time the federal government provided a formal channel for paradiplomacy.
- 2026: The UK-California MOU. Signed amidst a period of federal climate skepticism in the U.S., this agreement represents a direct bridge between a subnational entity and a sovereign foreign power, specifically focusing on the "green industrial revolution."
Supporting Data: The Economic Power of Subnational Actors
The influence of these subnational entities is underscored by their sheer economic and environmental scale. If California were a sovereign nation, it would currently rank as the fifth-largest economy in the world, with a GDP exceeding $3.8 trillion. Its regulatory decisions, such as the mandate to phase out the sale of new gasoline-powered vehicles by 2035, have a "Brussels Effect," forcing global manufacturers to adapt to its standards to maintain market access.
Similarly, the U.S. Climate Alliance states collectively account for more than 50% of the U.S. population and approximately 60% of the national economy. Data from the alliance suggests that its member states have managed to decouple economic growth from carbon emissions, reducing their collective greenhouse gas output by significantly higher margins than non-member states while maintaining robust employment in the clean energy sector.
On a global scale, the C40 cities are responsible for roughly 70% of global CO2 emissions. Their ability to implement local policies—such as congestion pricing, building retrofits, and waste management reforms—demonstrates that municipal action can achieve immediate, measurable results that national governments, bogged down by partisan gridlock, often cannot.
The Proposal for a Transatlantic Subnational Resilience Framework
As federal cooperation on climate change becomes increasingly volatile, experts are calling for a more structured approach to paradiplomacy. Jakob Wiedekind, a professor of political science and international relations at the University of North Carolina at Chapel Hill, has proposed the creation of a "Transatlantic Subnational Resilience Framework." Writing in the Georgetown Journal of International Affairs, Wiedekind argues that in the absence of federal commitment, new channels for cooperation must be established to ensure energy security and climate progress.
The framework is modeled on the European Union’s concept of "multi-level governance." A prime example is the REPowerEU initiative, launched in response to the 2022 energy crisis following the invasion of Ukraine. While the initiative was directed by the European Commission, its success relied on regional and local actors sharing expertise on how to rapidly deploy renewable energy and reduce reliance on imported gas.
Wiedekind suggests that a similar decentralized framework between the U.S. and Europe could focus on "climate-adjacent" topics. By centering discussions on disaster management—such as responding to the catastrophic wildfires in the American West or the devastating floods in Western Europe—proponents hope to depoliticize the dialogue. This strategy is intended to attract participation from leaders across the political spectrum, including Republican lawmakers in the U.S. who may be skeptical of "climate policy" but are highly invested in "resilience" and the economic benefits of clean-energy ventures.
Official Responses and Political Implications
The debate over these independent diplomatic tracks has split the political landscape. Supporters of subnational action argue that states have a moral and economic imperative to protect their citizens. "California is not going to wait for a permission slip from Washington to protect our people from the climate crisis," a spokesperson for the Governor’s office stated in response to federal criticism. "Our economy and our future depend on being leaders in the global energy transition."
Conversely, critics argue that such moves undermine the "one-voice" doctrine of American foreign policy. Legal scholars from conservative think tanks have warned that if states are allowed to negotiate their own international agreements, it could lead to a fragmented and incoherent national strategy, potentially emboldening foreign adversaries to play different states against the central government.
International partners, however, seem increasingly willing to engage with these smaller jurisdictions. For the United Kingdom and the European Union, partnering with California or New York provides a "hedge" against shifting federal policies in the U.S. It ensures that technical cooperation on hydrogen technology, carbon capture, and grid modernization continues regardless of who occupies the Oval Office.
Broader Impact and Future Outlook
The persistence of subnational diplomacy suggests that the global movement toward decarbonization has reached a level of momentum that is difficult for any single national administration to halt. The integration of global markets and the falling costs of renewable technologies have created an economic gravity that pulls subnational governments toward green policies.
However, the "subnational work-around" is not without its risks. Without federal backing, these agreements lack the enforcement mechanisms of formal treaties. They rely on voluntary cooperation and the alignment of market forces. Furthermore, the constant threat of federal litigation creates a climate of uncertainty that can deter long-term private investment in large-scale infrastructure projects.
As the "storm" of federal climate denial continues, the efforts of cities and states represent a vital holding action. Whether through the C40’s urban initiatives or California’s transatlantic agreements, subnational diplomacy is proving to be a resilient feature of the modern world. These entities are not merely filling a vacuum; they are redefining what it means to be a global actor in the 21st century. The outcome of this struggle between central authority and regional autonomy will likely determine the pace at which the world can meet its most pressing environmental challenges. For now, the message from the subnational level is clear: where national governments falter, local and regional leaders will step in to bridge the gap.
