This research project takes up one of the conspicuous phenomena of the post-Cold War world, namely intervention for the sake of promoting democracy, especially by the United States, and discusses its legitimacy in the light of state sovereignty in the international politics, the practical effect on the local situations, and American domestic political ideals of democratic decision-making. The case studies are mainly on American intervention through the National Endowment for Democracy, but other related policies such as foreign aid, military intervention and covert actions are also covered in analyzing the efficacy of democratization policies abroad. The same cases are also analyzed from the viewpoint of domestic policy deliberation, especially by the Congress both in the policy making and oversight, examining the linkage of domestic and international democracy. Finally, the preceding analyses will be placed in the international political context to present a new concept for legitimacy of intervening for democracy.