Abstract: Lanni surveys what is known about the law of war in ancient Greece, addressing the law's sources, content, and enforcement mechanisms. She argues that although there was a relatively effective law of war in ancient Greece, it did not encompass humanitarian ideals. Instead, the laws of war focused on protecting sacred objects and observances. Despite the central role played by religion and honor in the Greek laws of war, these laws were indifferent to considerations of mercy and the protection of noncombatants. Lanni next asks what insight the evidence from ancient Greece might give us in the ongoing debate over whether international law can ever truly restrain states. The traditional scholarly account of the Greek law of war would support the realist position. But Lanni argues that the Greek example, which includes instances where Greek states observed international norms that were clearly contrary to their interests, suggests one time and place where international law served as a meaningful check on state behavior.