Nearly a quarter century after the September 11, 2001 attacks, the U.S.-led war on terror remains a defining force shaping international law, human rights, and global security. While major combat operations in Afghanistan and Iraq have formally ended, the long-anticipated shift from a war paradigm to a law enforcement approach has yet to materialize. Instead, U.S. and allied counterterrorism activities persist worldwide, raising urgent questions about the role of law in enabling and sustaining armed conflict. Perpetual War and International Law brings together leading experts to confront the enduring legacies of the post-9/11 era and explore viable alternatives to the use of force. The volume traces how legal and policy frameworks have served to legitimize military action, eroding the boundary between war and peace. Contributors challenge prevailing interpretations of international law in an age of endless war and unconventional threats. Drawing on insights from law, ethics, and security studies, the volume critically examines how legal and normative precedents established during the war on terror continue to shape contemporary conflicts. It offers bold pathways for shifting from a global order rooted in force to one grounded in restraint and the rule of law. Perpetual War and International Law is a vital intervention, inviting readers to reimagine how international law can constrain violence in an increasingly conflict-ridden world. The Just Security book series from OUP tackles contemporary problems in international law and security that are of interest to a global community of scholars, policymakers, practitioners, and students. With each volume taking a particular thematic focus and gathering leading experts, the series as a whole aims to rigorously and critically reflect on developments in these areas of law, policy, and practice. Each volume will be accompanied by a series of shorter digital pieces in Just Security's online forum at www.justsecurity.org, which tie the discussion to breaking news and headlines.