Relationship of international law and municipal law — Act of State and justiciability — United States act of State doctrine — Rationale — Definition of act of State — Purpose of doctrine to prevent court adjudicating upon validity of foreign act of State — Action for defamation — Massacre at refugee camps in Lebanon — Magazine making allegations against former Minister of Defence in Government of Israel — Whether adjudication of claim barred by act of State doctrine — Relations between Israel and the United States — Relationship between act of State and political question doctrines — The law of the United States