States as international persons — In general — Recognition of acts of foreign States and governments — Act of State doctrine — Expropriation of property — Accounts at Saigon branch of New York bank — Branch closed shortly before decree of expropriation enacted — Situs of debts — Whether transferred to New York — Whether United States courts will give extraterritorial effect to expropriation decrees — Whether confiscation of corporation's assets extinguishes corporation — Date at which debts to be converted into United States currency — The law of the United States