International organizations — United Nations — Member of national delegation to United Nations — Whether presence in United States to attend United Nations session vests individual with immunity from suit

Jurisdiction — Acts of genocide and torture — Whether within jurisdiction of United States courts — Acts by unofficial Hutu political leader against Tutsi population in Rwanda — Acts committed in coordinated campaign of genocide with Government — United States Alien Tort Act vesting subject-matter jurisdiction in respect of all acts of genocide — United States Torture Victim Protection Act — Requirement that acts of torture and summary execution not constituting genocide be performed by State actor or under “color of law” — The law of the United States