This article investigates the law of Head of State immunity in the United States in light of the recent decision by the International Court of Justice in the Arrest Warrant Case (DRC v. Belgium). It does so by analyzing the U.S. law and comparing it with the customary international law on Head of State immunity as laid out by the world court. The article demonstrates that there are two competing strands in the recent jurisprudence of U.S. courts, neither of which is in conformity with international law. The reasons for this discrepancy are examined and explained in light of the underlying debate about the role of customary international law in the U.S. constitutional system. In conclusion, the author suggests that the best solution to the current dilemma is for the U.S. courts to apply the rules on Head of State immunity as explained by the world court and avoid as much as possible interference by the executive.