Sovereign immunity — Foreign States and government-owned corporations — Contracts for sale of oil between Libyan Government-owned corporation and foreign companies — Termination as a result of political measures by Libyan Government — Whether Libya and Libyan Government-owned corporation entitled to sovereign immunity — Whether actions having direct effect within the United States — Whether Libya amenable to suit under Act for allegedly inducing its national oil corporation to break contracts in order to comply with oil embargo — Whether Libya and its oil corporation amenable to suit for termination of contract between plaintiffs and oil concessionaire allegedly arising from nationalization — State responsibility — For revocation of concessions — Nationalization as a sovereign act — The law of the United States