Presently, a black flag with a skull-and-crossbones (the ‘Jolly Roger’) is merely a cultural icon for piracy. This chapter excavates the flag’s deep roots in international law. First, the chapter uncovers that the flag (and prior to it a red banner known as ‘Oriflamme’) used to be a laws-of-war signal for the intention to summarily execute captured enemy (‘take no prisoners’/’deny quarter’). It was used not only by pirates. Second, the chapter shows that intriguingly, the flag’s history aids in exposing misconceptions regarding criminal justice. Domestic criminal law is considered the traditional form of criminal justice, whereas, except for piracy, international crimes (meriting universal jurisdiction) are considered a novel, post-World War II, creation. However, historically, universal jurisdiction was applied not only to piracy, but also to felonies (crimes classified today as domestic) and war crimes. That actual history of criminal justice and the Jolly Roger’s legal history were forgotten for similar reasons.