War crimes are historically conceptualized as falling within two main categories: those concerned with the conduct of hostilities (including breaches of the rules governing the means and methods of warfare) and those concerned with custodial abuses against protected persons. The latter are commonly assumed to be easier to prosecute because the abuse is unjustifiable and often incontestable, and legal actors are not required to contend with the proverbial fog of war or to gain access to battlefield evidence. Nor do they require finders of fact to calculate whether any incidental harm to civilians was excessive in relation to the concrete and direct military advantage anticipated, as demanded by the intertwined principles of distinction and proportionality. Nonetheless, all war crimes are challenging to prosecute for a range of reasons, including the technicality of some constitutive elements, the difficulties of amassing sufficient available evidence to meet applicable burdens of proof, the vagaries of unreliable or unavailable witnesses, and the often impenetrable khaki wall of silence. Adding to these ubiquitous challenges, the United States has erected a number of idiosyncratic structural barriers in the way in which it has incorporated the prohibitions against war crimes into its domestic legal frameworks, both military and civilian. This paper, which will contribute to a new volume produced by West Point’s Lieber Institute for Law and Land Warfare, addresses problems with the United States’ federal war crimes statute as it appears in Title 18, the U.S. penal code, that have rendered the War Crimes Act a dead letter since its enactment in 1996. My recommendations for reform are directed at both Congress and the Executive Branch who should, within their respective spheres of competency, work to: (1) better conform the War Crimes Act to U.S. obligations under the 1949 Geneva Conventions and enable the United States to prosecute war crimes committed anywhere in the world regardless of the nationality of the victim or perpetrator, (2) withdraw and repudiate controversial Office of Legal Counsel (OLC) memoranda advancing a crabbed interpretation of the concept of “protected persons” when it comes to individuals in the custody of a High Contracting Party (HCP) to the Conventions, (3) restructure the statute to obviate the need to undertake a complicated conflict classification exercise, (4) enact a superior responsibility statute that would apply to war crimes and other international crimes within U.S. jurisdiction, and (5) re-penalize all violations of common Article 3. To lay a foundation for this close analysis of the U.S. War Crimes Act, this chapter sketches the way in which war crimes find expression in IHL, including in treaties to which the United States is a party and customary international law (CIL). It then provides a quick legislative history of the War Crimes Act of 1996 with references to the prevailing inter-agency dynamics and its advantages and shortfalls. It closes with a set of discrete drafting and policy recommendations to address the latter. Together, these amendments would bring the United States into better compliance with its treaty obligations and the rules adopted and applied by its NATO and other allies. It would likewise enable the United States to prosecute war crimes committed in all armed conflicts, whether international or non-international, and regardless of the nationality of the accused or victim. In so doing, it would strengthen complementarity arguments vis-a-vis international and national courts that might assert jurisdiction over U.S. persons. Finally, it would signal U.S. intolerance for deliberate harm to individuals who find themselves in the custody of a state to which they are not nationals and ensure that superiors do not escape legal censure when they know, or should have known, that their subordinates are committing, or have committed, abuses and they fail to take the necessary steps to prevent and punish these breaches.