Due to North Korea’s recent actions, some in Japan is advocating Japan to gain the ability to launch offensive attacks. This is a rare attitude in Japan, as most Japanese are pacifists because the aftermath of World War II. Japan is forbidden by their Constitution, written by Americans after World War II, to have an army to attack. Its military forces are only allowed to act in defense to a threat. The Japan-U.S Security Treaty provides for protection for Japan from the United States. Interestingly enough, the bilateral treaty makes several references to the the U.N charter and the Security Council. Such as Article V in the treaty:
Each Party recognizes that an armed attack against either Party in the territories under the administration of Japan would be dangerous to its own peace and safety and declares that it would act to meet the common danger in accordance with its constitutional provisions and processes. Any such armed attack and all measures taken as a result thereof shall be immediately reported to the Security Council of the United Nations in accordance with the provisions of Article 51 of the Charter. Such measures shall be terminated when the Security Council has taken the measures necessary to restore and maintain international peace and security.
According to the article, “Acquiring strike capability might be legally permissible under international law, but it will be difficult to sell to the Japanese public.” It seems the international law binding Japan to be unable to act on the offensive, is its own Constitution and the Japan-U.S. Security Treaty.
If Japan has the capability to launch offensive attacks, it is almost certain that China, North and South Korea, and other countries in the region will have issues.