UK-California Climate Alliance Set to Expand Despite Trump Opposition: A New Era of Sub-National Diplomacy

The Emerging Battle Over Sub-National Climate Diplomacy

A significant diplomatic confrontation is brewing between the White House and an unexpected alliance: the United Kingdom and California. On February 17, 2026, President Donald Trump launched a scathing attack on a clean energy agreement between UK Energy Secretary Ed Miliband and California Governor Gavin Newsom, calling the deal "inappropriate" and warning Britain against cooperation with the California governor (Articles 1-17). The memorandum of understanding (MOU), signed at London's Foreign Office, represents the 12th such agreement between the UK and individual U.S. states, following similar deals with Washington and Florida. The accord aims to boost transatlantic investment, strengthen research collaborations, support clean energy businesses accessing the California market, and share expertise on climate resilience.

Current Situation: A Constitutional Gray Zone

Trump's criticism centers on a fundamental constitutional question: whether U.S. state governors have the authority to engage in what amounts to international diplomacy. His complaint that it's "inappropriate" for governors to make international agreements—and for foreign nations to engage with them—touches on the delicate balance between federal and state powers in American governance. The UK government appears unmoved by Trump's objections. The deal proceeds independently from British efforts to negotiate energy policy with the Trump administration, suggesting London is pursuing a dual-track strategy: maintaining federal-level dialogue while simultaneously building partnerships with progressive state governments.

Key Trends and Signals

Several important patterns emerge from this confrontation: **1. The Rise of Sub-National Climate Diplomacy**: California's international climate engagement isn't new, but the UK's systematic approach—12 MOUs with various states—signals a formalization of sub-national climate cooperation. This suggests other nations may view American states as legitimate partners in the absence of federal climate action. **2. Trump's Personal Antagonism**: The president's use of derogatory nicknames ("Gavin Newscum") and sweeping criticisms ("everything he's touched turns to garbage") indicates this is personal as well as political. This emotional dimension suggests Trump may take concrete retaliatory actions rather than simply issuing rhetorical objections. **3. UK's Strategic Hedging**: By maintaining that this deal "sits separately from British efforts to find common ground on energy with Mr Trump's administration," the UK signals it won't allow federal-level difficulties to derail climate partnerships. This represents a sophisticated diplomatic strategy that acknowledges America's federal structure.

Predictions: What Happens Next

### Immediate Response (1-2 Weeks) Expect Trump to escalate beyond rhetoric. He may direct the State Department to formally protest the UK's sub-national engagement, potentially arguing it violates federal foreign policy prerogatives. Look for statements from the Secretary of State or formal diplomatic communications suggesting the administration views these agreements as undermining presidential authority. The Trump administration might also threaten to complicate ongoing UK-US trade negotiations or other bilateral initiatives. Given Trump's transactional approach to foreign relations, he's likely to seek leverage over Britain's broader relationship with Washington. ### Medium-Term Developments (1-3 Months) Other Democratic-governed states will likely accelerate their own international climate partnerships. New York, Washington, Oregon, Illinois, and others may announce similar MOUs with European nations, creating a de facto parallel climate diplomacy infrastructure. This would effectively bypass federal climate policy while Trump remains in office. The UK will almost certainly proceed with implementation, using the agreement as a template for expanded cooperation with other U.S. states. British clean energy companies and research institutions will begin establishing partnerships in California, creating economic facts on the ground that make the agreement harder to unwind. Republican governors and conservative legal scholars may file legal challenges or demand investigations into whether these state-level international agreements violate the Constitution's foreign affairs powers. However, precedent for state-level international cooperation on non-binding matters is well-established. ### Long-Term Trajectory (3-12 Months) This confrontation marks the beginning of a significant shift in international climate governance. If the UK-California partnership succeeds and expands, it could establish a new model where national governments increasingly work with sub-national entities in federal systems, effectively routing around recalcitrant central governments. The 2028 U.S. presidential election will become intertwined with this issue. If Newsom positions himself as a presidential candidate—as many speculate—his international climate leadership could become either a significant asset or liability depending on how Americans view his defiance of Trump. Conversely, if Trump administration attempts to punish the UK economically or diplomatically backfire, it could strengthen transatlantic progressive alliances and demonstrate the limits of presidential power over determined state actors and foreign partners.

The Broader Implications

This dispute transcends Trump versus Newsom or even climate policy. It represents a fundamental question about governance in an era of polarization: Can sub-national entities and foreign partners effectively create policy frameworks that circumvent national governments? The answer appears to be yes—and this UK-California partnership may be remembered as the moment when sub-national climate diplomacy came of age, creating a template for international cooperation that survives political changes at the national level. The real question isn't whether Trump can stop it, but whether he inadvertently accelerates it through his opposition.