The Peace Preservation Law was a Japanese law enacted on April 22, 1925, with the aim of allowing the Special Higher Police to more effectively suppress alleged socialists and communists. In addition to criminalizing forming an association with the aim of altering the kokutai of Japan, the law also explicitly criminalized criticism of the system of private property and became the centerpiece of a broad apparatus of thought control in Imperial Japan. Altogether, more than 70,000 people were arrested under the provisions of the law until its repeal by Allied occupation authorities at the end of World War II.

Kokutai is a concept in the Japanese language translatable as "system of government", "sovereignty", "national identity, essence and character", "national polity; body politic; national entity; basis for the Emperor's sovereignty; Japanese constitution" or nation.