In the fall 2007 Diet session, the largest opposition Democratic Party of Japan (DPJ) showed strong opposition against the government's proposal to continue the Self-Defense Forces (SDF) refueling operations to support maritime inspections in the Indian Ocean. In order to evaluate this parliamentary confrontation, the article compares the handling of this issue with the six past major post-Cold War national security policies. The DPJ constantly presented its own legislative proposals in order to participate in Diet deliberation. DPJ's counter proposals, however, were not always cooperative with the government. This different attitude by the DPJ could not be explained by the public and media opinions or the position of the supporting organization but by DPJ's political calculation.