The Japanese government wants permanent legal authority to send military forces overseas. Letting it have it would be a mistake for many reasons, but one seldom raised is the impact the move would have on the nature of Japan's democracy. A law conferring permanent authority to deploy troops would eliminate important institutional checks and balances on the government's use of the military, causing a further weakening of the separation of powers in Japan.
It would also run counter to the recent trend in other democracies to increase accountability in the process of deciding to use armed force.
As it stands now, the government (meaning the executive branch, the Cabinet) has to have specific legislation passed by the Diet, such as the Anti-Terrorism Special Measures Law (the ATSML), to obtain the required legal authority to deploy troops outside of Japan. A new law is required each and every time the government wants to dispatch the Self-Defense Forces (SDF), whether for the purpose of U.N. peacekeeping or to provide humanitarian support for collective security operations such as those in Afghanistan.