Sovereign immunity — Foreign States — Assassination of former Chilean government official in United States — Foreign Sovereign Immunities Act 1976, Section 1605 (a) (5) — Whether Chilean Government amenable to suit in United States courts for allegedly tortious activities concerning assassination — Whether exception to immunity for certain tortious acts of a foreign State and its officials or employees limited to “private” as opposed to “public” or “governmental” tortious acts — Whether Chile entitled to claim immunity under Section 1605 (a) (5) (A) — Whether allegedly tortious activities were “discretionary acts” — Whether Chile's activities were public activities within Chile — Whether entitled to immunity under act of State doctrine — The law of the United States