The latest revision to the guidelines on Japan-U.S. defense cooperation, formally agreed on in New York on Monday just as Prime Minister Shinzo Abe began his much-hyped visit to the United States, potentially expands the scope of the Self-Defense Forces' joint operation with the U.S. military on a global scale in ways that essentially transcend the original architecture of the postwar security treaty between the two countries. The government says such a transformation is essential for the alliance to effectively deal with the radically changing global security environment. It is questionable, however, whether there is a domestic political consensus on how far Japan is ready to expand its international security role.

The guidelines, updated for the first time in 18 years, are not legally binding on either country. To put the agreement into effect, Japan needs to enact a legislative package that has been prepared by the Abe administration to implement a Cabinet decision last July that paves the way for the nation to engage in collective self-defense — in a major departure from the nation's postwar defense posture — and significantly widen the scope of the SDF's overseas missions. Through debate on the security legislation, the Diet needs to fully explore the implications of the new guidelines, including what they entail for Japan and its security in concrete terms.

The guidelines, which establish a division of labor between the SDF and the U.S. military, were originally adopted in 1978 in the middle of the Cold War — and were primarily designed for joint operations in the event of an armed attack on Japan, with the most likely scenario being an invasion by Soviet forces.