The U.N. Charter is a cornerstone of international law, emphasizing its constitutional framework and multilateralism as essential components in maintaining global peace and security. This chapter highlights the U.N. Charter’s codification of international legal norms, traces the historical evolution of international law, and examines the Charter’s reliance on international institutions, including the International Court of Justice, to enforce legal principles and resolve disputes. The chapter also addresses the challenges of balancing state sovereignty with universal legal norms, underscoring the U.N. Charter’s role in advancing human rights and creating mechanisms like the International Law Commission. Key milestones in the development of international law, including the Nuremberg Principles, the Genocide Convention, and the Vienna Convention on the Law of Treaties, are discussed. These achievements illustrate the dynamic evolution of international law as a mechanism for justice, accountability, and cooperation in the global community. By examining the U.N. Charter’s historical origins, foundational legal structures, and ongoing influence, the chapter underscores its enduring significance as a “living document” that continues to shape and adapt to humanity’s aspirations for peace, dignity, and development.