Aaron J. Walayat | July 21, 2026
The international system is typically conceived of as a system of nation-states where each sovereign nation-state speaks with a singular voice. This presumption has recently been challenged by the rise of non-state actors, including, but not limited to, multinational corporations, such as Amazon or Foxconn, and international non-governmental organizations, such as Greenpeace or Human Rights Watch. Similarly, subnational actors, like cities and other administrative divisions including states or provinces, have also become active in international affairs.
The general consensus is that, under the United States Constitution, the federal government “alone may directly exercise power in foreign affairs.” Despite this, the Constitution still provides surprisingly wide latitude for states to participate in international affairs. California has been particularly active in its own international affairs. For a recent example, look no further than California’s response to President Donald Trump’s decision to withdraw from the World Health Organization (WHO).
U.S. Withdraws, California Collaborates
Shortly after his inauguration, President Donald Trump issued an executive order announcing his intention to withdraw from WHO. Because the treaty stipulated that withdrawal requires one-year of notice, the United States did not formally withdraw until January 22, 2026.
One day after the United States withdrew, on January 23, 2026, California Governor Gavin Newsom met with WHO Director-General Tedros Adhanom Ghebreyesus to “discuss collaboration to detect and respond to emerging public health threats.” As part of this collaboration, Governor Newsom announced that California would join the WHO’s Global Outbreak Alert & Response Network (GOARN). GOARN is “a WHO network of over 360 technical institutions and networks globally that respond to acute public health events with the deployment of staff and resources to affected countries,” with programs that aim to advance “emergency preparedness, response, and collaboration.” Governor Newsom’s announcement has been described by the media as a “rebuke” of President Trump’s withdrawal.
Governor Newsom’s decision to have California join a network affiliated with an international organization that the United States left raises legal questions related to preemption and the federal government’s power over foreign affairs. For instance, can a U.S. state, like California, independently collaborate with an international organization?
Do State Lines Really Disappear Abroad?
When it comes to international relations, a state is typically subsumed within the United States instead of functioning as a sovereign entity. This conventional view was stated in the United States Supreme Court’s 1937 decision in United States v. Belmont:
“In respect of all international negotiations and compacts, and in respect of our foreign relations generally, state lines disappear.”
Additionally, two clauses in Article I, Section 10 of the Constitution limit the extent to which states can conduct international relations. The Treaty Clause provides that “[n]o State shall enter into any Treaty, Alliance, or Confederation” and the Compact Clause provides that “[n]o State shall, without the Consent of Congress … enter into any Agreement or Compact with another State, or with a foreign Power[.]”
Despite these limitations, however, all fifty states conduct active international relations. Professor Ryan Scoville examines how the individual states maintain a diverse range of international commitments despite the limitations imposed by the Treaty and Compact clauses, which range from coordinating climate change policy with Canadian provinces to promoting investment with Chinese provinces and municipalities.
The Limits of the Treaty and Compact Clauses
States can maintain these commitments, in part, because the Treaty and Compact clauses provide states leeway in conducting both formal and informal international relations. In 2020, the United States sued California for an agreement pertaining to cap-and-trade programs between California and the Canadian province of Quebec. The agreement highlighted a shared commitment to reduce greenhouse gas emissions. While the agreement provided that California and Quebec would “exercise sole authority over their own policies,” both committed to engaging in regular consultation and notification regarding their cap-and-trade policies. The United States argued that this agreement violated the Treaty and Compact Clauses because the agreement bound California with a foreign jurisdiction.
With respect to the Treaty Clause, the district court found that the agreement was not a treaty. Relying on a line of Supreme Court cases, the district court held that “‘treaty’ is a term of art,” and that “[n]ot all international agreements may be ‘treaties’ in the constitutional sense.” Rather, treaties are “of a political character” for the purposes of Article I and describe agreements pertaining to “‘alliance for purposes of peace and war,’ ‘mutual government,’ the ‘cession of sovereignty,’ and ‘general commercial privileges.’” Meanwhile, this agreement explicitly recognized that Quebec and California would adopt their own targets and regulations and maintain the “sovereign right to maintain, modify, repeal, or revoke any of their respective program regulations or enabling legislation.” Since both California and Quebec retained this ability, they were effectively making policy next to each other and neither “mutual government” or “cession of sovereignty” occurred.
Next, with respect to the Compact Clause, the district court determined that the agreement did not amount to a compact. Applying a test established by the Supreme Court in Northeast Bancorp, Inc. v. Bd. of Governors of Fed. Reserve Sys., the district court determined that the agreement did not have the “classic indicia of a compact,” which includes “(1) provisions that required reciprocal action for the agreement’s effectiveness; (2) a regional limitation; (3) a joint organization or body for regulatory purposes; and (4) a prohibition on the agreement’s unilateral modification or termination.” Because both California and Quebec maintained the sovereign right to make their own policies and unilaterally withdraw, the agreement did not have the classic indicia of a compact.
Because the agreement did not violate either clause, the district court granted summary judgment in favor of California. As a whole, United States v. California suggests that a state will not violate the Treaty or Compact clause as long as it maintains the ability to set its own policies and unilaterally withdraw from the agreement. This narrow definition of “treaty” and “compact” provides states with quite a bit of flexibility to engage in international affairs.
Possibilities of Preemption
However, this does not mean that states have a free hand. A state’s policies cannot conflict with federal policy in foreign relations. While there is no “preemption clause” in the U.S. Constitution, “conventional wisdom” holds that Congress has the power to preempt state laws under the Supremacy Clause, the Commerce Clause, or the Dormant Commerce Clause.” Preemption typically requires invoking a congressional statute or treaty that conflicts with the state law on a particular issue or establishing that Congress intended to cover an entire subject matter leaving no room for state regulation. Foreign policy preemption is different in that it does not rely on an existing statute or treaty to preempt state law. It is enough that state law conflicts with federal policy.
Certainly, treaties can preempt state law. Zchernig v. Miller, for example, involved an Oregon state law which prohibited a nonresident alien from inheriting property unless they met certain conditions. The U.S. Supreme Court determined that the Oregon state law unconstitutionally intruded into the field of foreign affairs, which was reserved for the federal government, and held that the state’s enforcement of this statute was preempted because it conflicted with a treaty between the United States and East Germany.
Additionally, executive agreements, binding international compacts that are permissibly made by the President that do not require the two-thirds advice and consent of the Senate, can preempt state law as well. In American Insurance Ass’n v. Garamendi, for example, California passed a law which required insurers doing business in California to disclose information about insurance policies sold in Europe during the Holocaust. While there was no clear statement from the federal government disapproving of such laws, the Supreme Court determined that the California law was unconstitutional because it conflicted with the President’s foreign policy as expressed through executive agreements with Germany, Austria, and France that indicated an interest in resolving Holocaust-era claims through voluntary settlement instead of lawsuits.
Thus, while participation in an international organization might not be unconstitutional, specific state policies made per an agreement could be unconstitutional if they conflict with federal law or foreign policy.
Conclusion
Because California’s collaboration with GOARN is mainly cosmetic, it is likely to be constitutional. Given that GOARN is a network that aims to advance “emergency preparedness, response, and collaboration,” it is unlikely that the Treaty or Compact Clause will be violated by California’s collaboration. The Treaty Clause and the Compact Clause are not violated because collaboration does not involve mutual government or cession of sovereignty, such as an arrangement permitting a foreign partner to compel California to make or retain specific policy changes, and because California can unilaterally terminate its collaboration. Likewise, collaboration alone will probably not lead to preemption. However, it remains to be seen what policies California will pass pursuant to this new collaboration and whether they might be preempted.
However, the courts have permitted states to act with surprisingly wide latitude in engaging in international affairs, and though the United States, for the most part, speaks in one voice internationally, there are many opportunities for the individual states, like California, to make their own voices heard.