Sakata v. Japan, 13 Keishu 3225 (Dec. 16, 1959), popularly known as the "Sunakawa Case," was one of the first major court decisions concerning Article 9, the so-called "peace clause" of the Japanese Constitution of 1946. Article 9 says:
Aspiring sincerely to an international peace based on justice and order, the Japanese people forever renounce war as a sovereign right of the nation and the threat or use of force as means of settling international disputes.
In order to accomplish the aim of the preceding paragraph, land, sea, and air forces, as well as other war potential, will never be maintained. The right of belligerency of the state will not be recognized.
Despite renouncing war and war potential, Japan procured guns and bombs a few years after the Constitution was enacted, first through the National Police Reserve of 1950, then through the Japan Self-Defense Forces of 1954. Through these defense reforms, Japan also hosted a large military presence from the United States, which provided the country's sole armed protection in the late 1940s and the lion's share of its protection for decades afterward.
Which brings us to the city of Tachikawa, located in the western suburbs of Tokyo. In the late 1950s, Tachikawa hosted a large United States Air Force base, Tachikawa Air Base. Although the site has now been turned into a park (somewhat ironically called the Showa Memorial Park) and SDF drill ground, it was, back then, one of the major U.S. bases in the Pacific. And since the U.S. liked big airplanes, Tachikawa's little runways needed to be expanded.
The runway expansion proposal required the Japanese government to acquire a large piece of farmland in a town called Sunakawa, just north of Tachikawa (today, it is part of the city). Unfortunately for the American and Japanese authorities, some of the locals in Sunakawa did not want to cooperate. As soon as surveyors hit the ground in Sunakawa on July 8, 1957, they were attacked by a mob, which found its way onto the airbase itself. Seven of the rioters were then arrested and charged with trespassing on an American military base, a felony under Japanese law ("regular" trespassing is a misdemeanor).
The Sunakawa Seven were tried in the Tokyo District Court, and found not guilty on March 30, 1959. The Court determined that the trespassing law was invalid, because it had been passed as an enforcement provision to the Japan-United States Security Treaty of 1951, which was a violation of Article 9 because it permitted the maintenance of military forces on Japanese soil.
Believing this decision to be completely legally unsound, the prosecutors filed an appeal directly to the Supreme Court of Japan, which reversed the decision and ordered the rioters to be penalized. Besides stating that the Diet possessed broad legislative discretion (as is generally accepted in Japanese law), the Supreme Court also held that the forces allowed in Japan under the Treaty were not forces of "war."
It is proper that our country, in the exercise of an inherent national function, be able to take the measures necessary for self-defense so that we can maintain our own peace and security, and preserve our existence. (We) do not maintain what is termed "war potential" in Article 9, but we have determined to preserve our peace and security... Article 9 does not at all prohibit a request to another country for security guarantees for the maintenance of the peace and safety of Japan.
So Japan's self-defense was officially deemed constitutional, and Japan went on to develop one of the largest armed services in the world.