The areas of defense and security are the key modern-day controversies revolving around the Constitution, which took effect 50 years ago May 3.

The key issue centers around the type of logistical support the Self-Defense Forces should be permitted to provide to the U.S. military in areas around Japan. The Japanese government officially views the use of the collective self-defense right as a constitutional trespass.

The ongoing review of the 1978 guidelines for Japanese-U.S. defense cooperation, which Tokyo and Washington want to conclude in September, has mainly been focusing on the SDF's logistical support. Although the prime minister has reassured that the changes would be kept in the framework of the Constitution, the Social Democratic Party, one of the two non-Cabinet allies in Hashimoto's ruling Liberal Democratic Party, is worried that the review may produce loose constitutional interpretations. The Japanese Communist Party opposes conducting a review on the grounds of protecting the Constitution.

But other lawmakers, such as Ichiro Ozawa, president of the main opposition party, Shinshinto, claim that exercising the right of collective self-defense is allowable under the Constitution.

Collective self-defense is the right of a country to use force to counter attacks being made on a foreign country with which it is closely linked, even if the country itself is not being attacked. How to interpret Article 9 is the center of most debate. The article bans use or the threat of force as a means of settling international disputes. Political parties have recently been looking closer at the possibility of changing the Constitution, and that has broken Japan's decades-long taboo on discussing a change to the charter.