International organizations — Immunity — Representatives of Member States — Scope of immunity — United Nations Industrial Development Organization (“UNIDO”) Headquarters Agreement, 1967, Article XI — Immunity limited to representatives of Member States “having official business with UNIDO” — Meaning — Question of whether representative acting within scope of activities of UNIDO — Whether dependent on view of UNIDO or sending State — Whether requiring decision of UNIDO recognizing status of person in question as a State representative entitled to diplomatic immunity

Diplomatic relations — Special missions — “Ad hoc” mission to international organization — Determination of status — UNIDO Headquarters Agreement, 1967 — Rules of customary international law — Whether such mission capable of coming into existence without consent of international organization concerned — The law of Austria