In April 1994, two surface-to-air missiles shot down a plane flying over the Rwandan capital of Kigali, killing Rwanda's then president, Juvénal Habyarimana, and his fellow Hutu tribesman, Cyprien Ntaryamira, who was the president of neighboring Burundi. Their deaths sparked a genocide by hard-line Hutus that cost nearly a million Tutsis and moderate Hutus their lives. When the slaughter ended, a Tutsi named Paul Kagame, leader of the Rwandan Patriotic Front, emerged as the president of Rwanda. But questions have lingered since 1994 that Kagame and his compatriots were responsible for the crash. There have been Rwandan and international investigations about who was behind the fateful missile shots but no definitive answers.

Nor will there be any in the United States, thanks to a 10th Circuit Court of Appeals decision on Oct. 10 that said the U.S. State Department has the right, under the Separation of Powers doctrine, to confer immunity on foreign heads of state. The opinion marks the first time a federal appeals court has interpreted foreign sovereign immunity since the U.S. Supreme Court decided in the 2010 case Samantar v. Yousuf that the Foreign Sovereign Immunities Act of 1976 protects foreign governments, but not individual foreign officials, from suits in the United States.

Kagame had been sued by the widows of Habyarimana and Ntaryamira, who filed their wrongful death and Alien Tort Statute case in federal court in Oklahoma City in April 2010. (Neither of the women lives in the United States, let alone Oklahoma, but Rwanda has an affiliation with Oklahoma Christian University; the women's lawyer, Peter Erlinder of the International Humanitarian Law Institute, actually attempted to serve Kagame with the complaint when Kagame spoke at the university in May 2010.) The Republic of Rwanda eventually requested what is known as a Suggestion of Immunity from the State Department. In August 2011, the U.S. government asked U.S. District Judge Lee West to grant Kagame immunity as the head of a foreign state.

Such immunity, according to Kagame counsel Pierre-Richard Prosper of Arent Fox, is the bedrock of foreign relations; if the United States didn't offer protection to foreign leaders, our own officials might be subject to litigation, or even arrest, in foreign courts. (Prosper, who is a former State Department ambassador-at-large on war crimes issues, is something of an expert on this topic.) But there was a wrinkle: In the Supreme Court's 2010 ruling in Samantar, the justices said that the Foreign Sovereign Immunities Act does not apply to individuals but only to foreign governments as a whole.

In that case, a former Somali prime minister accused of torture and other human rights violations claimed he was immune under the FSIA. The Supreme Court said he was not. But unlike Kagame, the Somali defendant, Bashe Yousuf, had not received a Suggestion of Immunity from the State Department, which was apparently reluctant to legitimize any Somali government official. That Suggestion of Immunity, West ruled in the Oklahoma case against Kagame, made all the difference.

"Where the United States' Executive Branch has concluded that a foreign head of state is immune from suit, and where it has urged the court to take recognition of that fact and to dismiss the suit pending against said head of state, the court is bound to do so," West wrote in an opinion in 2011.

The widows appealed to the 10th Circuit, arguing that U.S. heads of state are subject to tort claims, and so foreign officials should be as well. (The appellate brief also claimed that Kagame counsel Prosper strong-armed United Nations investigators to drop their case against Kagame; Prosper said he had no authority over the UN investigation, which never produced a report on the 1994 crash.)

The 10th Circuit sided with the argument Kagame and Arent Fox presented in their appellate brief, without even hearing oral arguments. "We must accept the United States' suggestion that a foreign head of state is immune from suit -- even for acts committed prior to assuming office," wrote Judge Bobby Baldock for a panel that also included judges Timothy Tymkovich and Neil Gorsuch.

It would have been surprising if the court had held otherwise, said Prosper, considering the longstanding principle that foreign officials must be immune from suits. "Obviously, we're pleased with the result," he said. "It confirms that foreign heads of state will be respected by our courts and that there will be reciprocity for our officials." (I called and emailed the widows' lawyer, Erlinder, but didn't hear back.)

As for the enduring question of which forces fired the missiles that brought down the Hutus' plane in 1994, Prosper said it will probably never be answered, considering the length of time that has now passed without definitive conclusions. "It will go down in history as an unsolved mystery," he said.

(Reporting by Alison Frankel)

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