This publication sets out fundamental principles of international and domestic law that govern U.S. naval operations at sea. This publication is intended for the use of operational commanders and supporting staff elements at all levels of command. It is designed to provide officers in command and their staffs with an overview of the rules of law governing naval operations in peacetime and during armed conflict. The explanations and descriptions in this publication are intended to enable naval commanders and their staff to comprehend more fully the legal foundations upon which the orders issued to them by higher authority are premised and better understand the commander’s responsibilities under international and domestic law to execute their missions within that law.