In 1955, the US government decided to enlarge several existing bases in Japan, including the Tachikawa base in Sunagawa. However, local residents were strongly opposed to the enlargement of this base, and this led to large protests. In July 1957, approximately 300 demonstrators broke through the fences of Tachikawa, trespassing onto the base. Seven of the demonstrators were arrested for breaking a special criminal law. The lawyers for the defendants claimed that the Japan-US Security Treaty that allowed US military personnel to be stationed in Japan violated Article 9 of the Japanese Constitution, which forbids Japan from maintaining forces to fight wars.
In March 1959, Tokyo District Court Judge Akio Date found that the US forces stationed in Japan could be considered “forces,” and thus were unconstitutional. He found all the defendants innocent. However, the District Attorney appealed the verdict to the Supreme Court. At the Supreme Court, basically two things were debated: (1) Does the constitution allow a foreign military (e.g., the US military) to be stationed in Japan? and (2) Is the Japan-US Security Treaty constitutional? Regarding the first argument, the judges found that foreign militaries in Japan were not “forces” forbidden by Article 9, paragraph 2. Therefore, a foreign military can be stationed in Japan. On the Japan-US Security Treaty, the judges avoided deciding its constitutionality, claiming that it is too political for the court to decide. They used the principle of 統治行為論 (tochikoiron). Tochikoiron allows the court to avoid issuing a legal ruling on something due to its highly political nature. 統治 means to govern, 行為 means action and 論 means theory.
The Sunagawa case is the most famous case where the Supreme Court used the principle of tochikoiron. The Sunagawa case is also known for LDP’s recent justification that the right to collective self-defense is constitutional. The fifth paragraph of the Supreme Court opinion says that “It is an exercise of an inherent right for our country to be able to take measures that are necessary for self-defense to maintain its peace and safety.” The LDP interprets the phrase “measures that are necessary for self-defense” to include the right to collective self-defense. However, many constitutional scholars claim that the Sunagawa case did not specifically reference the right to collective self-defense and thus the LDP cannot justify the right to collective self-defense using the Sunagawa case.