International organizations — Immunity — Jurisdictional immunity — Food and Agriculture Organization of the United Nations (“FAO”) — Lease — Action to secure rent increase — Whether FAO entitled to jurisdictional immunity — Constitution of FAO 1945, Article XV — FAO-Italy Headquarters Agreement, 1950, Article VIII, Section 16 — Scope of immunity of FAO from legal process — Whether application of general rules of customary international law on immunity of international organizations excluded by specific treaty provisions on immunity of FAO

International organizations — Immunity — Waiver — Conclusion of tenancy agreement by international organization — Whether constitutes waiver — Application to municipal courts by lessor for rent increase — Arbitration clause in tenancy agreement — Whether a bar to jurisdiction of municipal courts

International organizations — Legal status — Constitution of FAO, 1945, Article XV — The law of Italy