Operation ALLIED FORCE, the NATO air campaign in Kosovo, revealed the legal, moral, and political tensions that leaders must address when contemplating a humanitarian intervention. State sovereignty is protected under Chapter I, Article 2 of the United Nations (UN) Charter. The Charter provides limited specific exceptions for a state to use armed force against another state, with UN Security Council authorization. Meanwhile, a developing body of human rights law and numerous "humanitarian interventions" provide a growing challenge to state sovereignty. Addressed are the international legal issues that emerge when a state uses armed forces to halt gross human rights abuses by another state, as in Operation ALLIED FORCE. The discussion also evaluates the moral and political tensions that occur in humanitarian interventions in the context of the just war tradition. Jus ad bellum principles of just cause, proportionality, reasonable chance of success, and last resort, help determine whether a specific intervention, like Operation ALLIED FORCE, meets just war standards before action occurs. Finally, political considerations constrain the ability of states to consistently intervene when a just cause is present. The US-developed criteria for peacekeeping in Presidential Decision Directive (PDD) 25, and British Prime Minister Tony Blair's five guidelines for intervention are considered in relation to Operation ALLIED FORCE. Recognition of the legal, moral, and political dimensions to humanitarian interventions may help leaders form prudent decisions before committing armed forces to these operations.