State immunity — Jurisdictional immunity — Head of State — Requirement that defendant be identified as Head of State — Member of Royal Family in direct line of succession — Officials — Immunity for acts undertaken in official capacity — Criteria for determining whether act undertaken in official or private capacity — Claim in tort

States — Head of State — Entitlement to sovereign immunity — United Arab Emirates — Abu Dhabi — Abu Dhabi Royal Family

Relationship of international law and municipal law — Act of State doctrine — Limits of act of State doctrine in United States law — Relationship between act of State and State immunity — The law of the United States