International law supports order in the world and the attainment of humanity's fundamental goals of advancing peace, prosperity, human rights, and environmental protection. Yet, there have been voices for centuries attacking international law in order to promote the dominance or hegemony of a single nation. After 9/11, such advocates succeeded in getting America's leaders to invade Iraq, establish Guantanamo Bay and black sites, use waterboarding and other forms of torture and coercion during interrogation, and execute individuals in defiance of the International Court of Justice. This book reveals that to be persuasive, opponents of international law have misrepresented what international law is and how it works. Anti-international law voices have presented international law as powerless and unworthy of respect. To clear away the myths, the book draws on new developments in natural law, positive law, and process theory. The resulting new classical theory demonstrates that international law's power or authority is explained by the same theory that explains the authority of law within nations. International law has authority because it is widely accepted as law. Part of the evidence of that acceptance is found in the fact international law has forceful means of enforcement — armed force, sanctions, countermeasures, and courts. The book provides many examples of international law in action — the real international law with the power to support the interest of all humanity.