Japan’s Capital Construction Law, enacted in 1950, was intended to create the ability to obtain special financial assistance from the state to break the impasse of Tokyo’s reconstruction by regarding its planning and development as a national undertaking. However, recent studies in Japan’s planning history claim that the law was an infringement of local autonomy. This article considers how this law was discussed in the National Diet, which enacted it, and in a local referendum among Tokyoites as well as how its original proponents, particularly the metropolitan government planner Hideaki Ishikawa, who created the reconstruction plan for Tokyo, justified it.