Justin Yang is a junior at the University of Pennsylvania studying Politics, Philosophy, and Economics.
After President Trump announced he was planning to pull the United States out of the Paris climate accord, several states announced that they would defy the president and adhere to the accord themselves. In particular, California has tried to step up and fill the void the United States has left behind, meeting and striking climate deals with foreign governments like China.  In addition, a New York Times report revealed that governors are increasingly conducting the diplomacy they believe the Trump administration is neglecting: they are going abroad and meeting with foreign leaders, assuring them of America’s stance on climate change and trade.  All of these developments raise an interesting question: can a state conduct what appears to be foreign policy without the federal government?
The Constitution does not explicitly grant the power to conduct foreign policy in general to any particular institution, but it gives to the President power to negotiate treaties, to lead the armed forces, and to receive foreign ambassadors.  It also grants Congress the power to approve of treaties, the military budget, and the President’s nominee for the Secretary of State, as well as the power to regulate commerce with foreign nations and to declare war.  All this seems to imply that the federal government has the exclusive right to conduct foreign policy, a view that the Supreme Court has long held. In 1840, the Court held in Holmes v. Jennison that “it was one of the main objects of the constitution to make us, so far as regarded our foreign relations, one people, and one nation; and to cut off all communications between foreign governments, and the several state authorities.” 
There are wide areas of permitted state law that can have an important impact on foreign relations. For example, many states have pension funds that they use to invest in nations across the world, including nations which may have questionable human rights records or a negative relationship with the United States – it would not be surprising if a pension fund held stocks from a Chinese company.  These pension funds can also hold a considerable sway in global financial markets, and states can use this influence in political ways. In the 1980s, thirty-two states enacted what are, in effect, sanctions against South Africa for its apartheid policy through partial or total divestments of companies doing business in South Africa and bans on new investments.  States like Rhode Island and New York have investment policies that require companies in Northern Ireland to follow the MacBride Principles, which protect the Catholic minority from employment discrimination.  All this can have the effect of changing America’s relationship with these countries, as well as influence their policy outcomes.
While states are perfectly entitled to, for example, create a pension fund and make the necessary investment decisions, their influence on foreign affairs seems to infringe on the federal government’s exclusive right in this area. Such an exclusive right logically means that any state law that impinges on foreign relations, even when there is no relevant federal policy, must be struck down as unconstitutional, and this is exactly what the Supreme Court has held in previous cases.
For example, in a 1968 case, Zschernig v. Miller, the Court invalidated an Oregon law preventing the inheritance of a deceased American without heirs from going to citizens of Communist countries.  Although the Justice Department’s amicus brief denied that the law would cause “undue interference” in U.S. foreign policy, the Court said that there will still be a “persistent and subtle” effect when other countries see state courts denying payments to citizens of Communist countries.  Even though inheritance law is under the purview of the states, any restraints on citizens of those Communist nations “must be provided by the Federal Government.”  Justice Stewart, in response to the Justice Department’s amicus brief, put it in even stronger terms in his concurrence: “[t]oday, we are told, Oregon’s statute does not conflict with the national interest. Tomorrow it may.” 
Of course, Zschernig does not elaborate a clear standard on when a state law is considered to impinge on foreign relations. In 1994, the Supreme Court ruled in Barclays v. Franchise Tax Board that a California corporate tax formula that included worldwide revenue did not violate the Foreign Commerce Clause, because Congress’ inaction in this area implicitly permitted state action.  This ruling shows just how unclear the line between state law and federal foreign policy is, and it left the lower courts grappling with how to establish such a line.
As states become ever bigger and more important economic actors on the global stage, it is inevitable that many of their actions will have an effect on American foreign affairs. The aforementioned deal between California and China was on establishing a shared cap and trade market on carbon emissions, something that can arguably violate the federal government’s right to conduct foreign policy. But globalization means that many aspects of state law that have long been considered to be under the states’ purview will bump up against the federal government’s exclusive right to conduct foreign policy; and as states become more connected to the world, more and more of their interests will be tied up with other countries, and they will begin to demand a voice on the global stage. This will surely create more state actions that can run contrary to federal policy, and it is imperative that a clear line be drawn to protect both the state and federal governments’ rights and interests.
 “China and California sign deal to work on climate change without Trump.” The Guardian, June 6, 2017. Accessed July 16, 2017. https://www.theguardian.com/us-news/2017/jun/07/china-and-california-sign-deal-to-work-on-climate-change-without-trump
 Burns, Alexander. “Going Around Trump, Governors Embark on Their Own Diplomatic Missions.” New York Times, July 15, 2017. Accessed July 16, 2017. https://www.nytimes.com/2017/07/15/us/trump-governors-diplomatic-missions.html
 “The Constitution of the United States.” United States National Archives. Accessed July 16, 2017. https://www.archives.gov/founding-docs/constitution-transcript
 “Holmes v. Jennison.” Justia. Accessed July 16, 2017. https://supreme.justia.com/cases/federal/us/39/540/case.html
 Head, Carol E. “The Dormant Foreign Affairs Power: Constitutional Implications for State and Local Investment Restrictions Impacting Foreign Countries.” Boston College Law Review 42 (December 2000): 123-172. Accessed July 16, 2017. https://www.bc.edu/content/dam/files/schools/law/lawreviews/journals/bclawr/42_1/03_FMS.htm
 “State Laws Affecting Foreign Relations – Dormant Federal Power and Preemption.” Justia. Accessed July 16, 2017. http://law.justia.com/constitution/us/article-2/26-dormant-foreign-relations.html
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