Arbitration — Obligation to arbitrate — Dispute — Dispute concerning the interpretation or application of treaty — Agreement between the United States and the United Nations regarding the Headquarters of the United Nations, 1947 — Obligations of United States as host State — Palestine Liberation Organization (“PLO”) Observer Mission to United Nations — United States Anti-Terrorism Act 1987 — Whether requiring closure of PLO Observer Mission — Whether requirement of closure would be contrary to 1947 Agreement — Implementation of Anti-Terrorism Act irrespective of Headquarters Agreement — Whether amounting to a dispute about the interpretation or application of the Agreement — Crystallization of dispute — whether enactment of Anti-Terrorism Act creates a dispute without enforcement of Act

International Court of Justice — Advisory jurisdiction — Request for opinion on whether the United States and the United Nations required to submit dispute to arbitration — Extent of question before the Court — Court not asked to rule upon underlying dispute

International organizations — Headquarters agreements — United Nations — Agreement between the United States and the United Nations regarding the Headquarters of the United Nations, 1947 — Obligations of the host State — Possible closure of PLO Observer Mission to United Nations pursuant to United States Anti-Terrorism Act 1987 — Whether United States required to submit dispute to arbitration

Relationship of international law and municipal law — Treaties — Effect in municipal law — Agreement between the United States and the United Nations regarding the Headquarters of the United Nations, 1947 — Possible conflict with the Anti-Terrorism Act 1987 — Whether priority to be accorded to treaty

Treaties — Application — Conflict with municipal statute — Agreement between the United States and the United Nations regarding the Headquarters of the United Nations, 1947 — United States Anti-Terrorism Act 1987 — Whether United States required to comply with treaty irrespective of conflict with later statute — Principle that State cannot rely upon municipal law as justification for non-compliance with treaty — Whether conflict between treaty and statute raises a dispute regarding the interpretation or application of the treaty