Sovereign immunity — Foreign State-owned corporations — Central bank — Restrictive theory of sovereign immunity — Commercial activity — Acts characterized by reference to their nature rather than their purpose — Need to consider acts upon which claim based rather than general activities of foreign entity — Whether central bank had acted in commercial capacity in issuing cheque drawn on a foreign bank or in exercise of governmental function of regulating foreign exchange — Exception to immunity in cases of confiscation of property in breach of international law — Exception to immunity in respect of tortious conduct causing injury in the United States — Whether tortious conduct has to take place inside the United States — Scope of Foreign Sovereign Immunities Act 1976 — Whether going beyond restrictive theory — Burden of establishing immunity — Act of State doctrine — The law of the United States