Abstract: Courts have often advertised an ability to determine when a suit is "really" against a state, or a tax or regulation is "really" a burden on a federal instrumentality. The conceptual difficulties of the holdings in each area suggest, however, that this advertising is largely deceptive. In this Article, Professor Tribe argues that attention to the question of who should decide an intergovernmental immunity issue - the states, the federal courts, the federal executive, or Congress - illuminates the law of eleventh amendment immunities and intergovernmental tax and regulatory immunities and supports all but a handful of the results courts have reached. By reserving to Congress the ultimate authority to determine intergovernmental immunities, he concludes, courts have ensured that the interests of the states as separate sovereigns will receive due weight in the formulation of national policy.