Sovereign immunity — Foreign States — Contract for sale of goods — Assumption of responsibility for performance of contract by foreign State following nationalization measures — Whether entitled to jurisdictional immunity — Acts iure gestionis and iure imperii — Relevance of State monopoly of economic activity — Whether State legislative activity a sovereign activity — Whether nationalization without compensation can be recognised in municipal courts — Whether damage caused to private interests by such activity creates directly enforceable rights for individuals under international law — The law of Italy