If Vladimir Putin is prosecuted or sued in the United States, is he entitled to head-of-state immunity? In the past, the U.S. government has maintained that the executive branch has the constitutional power to make foreign official immunity determinations that are binding on state and federal courts. In other words, the government’s position is that President Trump would have absolute power to decide which sitting and former government officials—including heads of state such President Putin—are immune from suit in the U.S. on a case-by-case (or even moment-to-moment) basis.

Long before Trump became president, I argued that the government’s view was incorrect as a matter of constitutional law and unwise as a policy matter. The policy dangers have only become clearer since Trump was elected. President Trump’s foreign business dealings and his own exposure to suit in foreign courts, Russian meddling in U.S. elections and cybersecurity more broadly, as well as the President’s thin-skinned, personal style of politics all illustrate the dangers of allowing the executive branch to make foreign official immunity determinations binding on the courts.

Here is how foreign official immunity works. In the United States, the immunity of foreign states from suit in both state and federal court is governed by a federal statute, the Foreign Sovereign Immunities Act (FSIA). But the Supreme Court has held that the FSIA does not apply to claims against individual foreign officials, which are governed instead by common law (presumably federal common law). Under customary international law, sitting heads of state are entitled to personal immunity from all claims brought in foreign courts—meaning that international law protects President Trump from suits abroad. International law affords former heads-of-state, as well as lower level officials (both sitting and former), a more limited kind of immunity for their official acts. Sir Christopher Greenwood, a judge on the International Court of Justice, provides an introduction in this video. In courts in the United States both kinds of individual immunities are governed by common law. The executive branch maintains that if it makes an immunity determination (yea or nay), the courts are constitutionally bound to accept that determination. That argument is deeply flawed on legal grounds. Here, however, I wish to focus the policy problems with executive branch immunity determinations.

As a policy matter, a State Department—or a President—that makes immunity determinations will likely face pressure from foreign entities seeking immunity before U.S. courts. Although historically the State Department has made immunity determinations, there is nothing that prevents the President from doing so instead. Foreign interests might pressure President Trump to make favorable immunity determinations for a number of reasons. Trump may have business incentives to protect foreign officials from suit in U.S. courts. For example, he might want a trademark in another country or he may wish to himself avoid suit in a foreign country. Or President Trump could have personal or political reasons to protect foreign officials such as Putin. These dangers are heightened by President Trump’s thin-skinned, retribution-oriented style of leadership. Indeed, he could deny immunity to foreign heads-of-state and other officials simply because they offended him or he otherwise does not like them.

The history of immunity illustrates that these concerns are not merely hypothetical. Executive branch immunity determinations have invited pressure from foreign entities in the past. Before enactment of the FSIA, the executive branch had the power to make immunity determinations in cases against foreign states. It did not work well, as former State Legal Adviser Harold Koh explains here. Foreign governments exerted diplomatic pressure on the State Department to resolve cases in their favor, which in turn generated more pressure from other governments. The practice also generated complaints about inconsistency and favoritism from both governments and private litigants. The possibility of foreign pressure around immunity issues is illustrated by the wide variety of defendants who have benefited from immunity including Chinese President Jiang Zemin; President Biya of the Republic of Cameroon; President Mugabe of Zimbabwe; former President of Mexico, Ernesto Zedillo Ponce de Leon; and the former directors of the Pakistani Inter-Services Intelligence Directorate, as described by John Bellinger here.

To be sure, suits against foreign officials, including foreign heads of state, encounter other obstacles such as personal jurisdiction and enforcement of resulting judgments. Head of state and other forms of official immunity nevertheless serve important purposes, including the sovereign equality of states, international comity, and the facilitation of diplomatic relations. As a matter of constitutional law and policy, courts in the United States should apply federal common law to foreign official immunity determinations and not treat executive statements or suggestions of immunity as controlling.

Originally posted on lawfareblog.com.