After 1898 the United States not only solidified its position as an economic colossus, but by annexing Puerto Rico and the Philippines it had also added for the first time semi-permanent, heavily populated colonies unlikely ever to attain statehood. In short order followed a formal protectorate over Cuba, the "taking" of Panama to build a canal, and the announcement of a new Corollary to the Monroe Doctrine, proclaiming an American duty to "police" the hemisphere. Empire had been an American practice since the nation's founding, but the new policies were understood as departures from traditional methods of territorial expansion. How to match these actions with traditional non-entanglement constituted the central preoccupation of U.S. foreign relations in the early twentieth century. International lawyers proposed instead that the United States become an impartial judge. By becoming a force for law in the world, America could reconcile its republican ideological tradition with a desire to rank with the Great Powers. Lawyers' message scaled new heights of popularity in the first decade and a half of the twentieth century as a true profession of international law emerged. The American Society of International Law (ASIL) and other groups, backed by the wealth of the Carnegie Endowment for International Peace, held annual meetings and published journals. They called for the creation of an international court, the holding of regular conferences to codify the rules of law, and the education of public opinion as to the proper rights and duties of states. To an extent unmatched before or since, the U.S. government-the executive branch if not always the U.S. Senate-embraced this project. Washington called for peace conferences and pushed for the creation of a "true " international court. It proposed legal institutions to preserve order in its hemisphere. Meanwhile lawyers advised presidents and made policy. The ASIL counted among its first members every living secretary of state (but one) who held office between 1892 and 1920. Growing numbers of international lawyers populated the State Department and represented U.S. corporations with business overseas. International lawyers were not isolated idealists operating from the sidelines. Well-connected, well-respected, and well-compensated, they formed an integral part of the foreign policy establishment that built and policed an expanding empire.

America's empire expanded dramatically following the Spanish-American War of 1898. The United States quickly annexed the Philippines and Puerto Rico, seized control over Cuba and the Panama Canal Zone, and extended political and financial power throughout Latin America. This age of empire, Benjamin Allen Coates argues, was also an age of international law. Justifying America's empire with the language of law and civilization, international lawyers-serving simultaneously as academics, leaders of the legal profession, corporate attorneys, and high-ranking government officials-became central to the conceptualization, conduct, and rationalization of US foreign policy. Just as international law shaped empire, so too did empire shape international law. Legalist Empire shows how the American Society of International Law was animated by the same notions of "civilization" that justified the expansion of empire overseas. Using the private papers and published writings of such figures as Elihu Root, John Bassett Moore, and James Brown Scott, Coates shows how the newly-created international law profession merged European influences with trends in American jurisprudence, while appealing to elite notions of order, reform, and American identity. By projecting an image of the United States as a unique force for law and civilization, legalists reconciled American exceptionalism, empire, and an international rule of law. Under their influence the nation became the world's leading advocate for the creation of an international court. Although the legalist vision of world peace through voluntary adjudication foundered in the interwar period, international lawyers-through their ideas and their presence in halls of power-continue to infuse vital debates about America's global role