While the Japanese government affirmed Japan had a basic right to defend itself, it denied Japan’s right to collective self defense. While most governments — and even the United Nations — recognize a state’s right to collective self-defense, Japan declines on the grounds that it may involve Japan in military action not directly pertaining to Japan’s self-defense or action offensive in nature. Such action would be unconstitutional. The Self Defense Forces can only act on threats to Japan and not other countries.
“Japanese Government Recommends Major Defense Policy Change“, USNI News, 5/15/14.