Fears that newly enfranchised working-class voters might vote for socialists or communists played an important role in overcoming earlier opposition to the law.

In 1927, a sub-bureau, the "Thought Section," was established within the Criminal Affairs Bureau of the Special Higher Police within the Home Ministry in order to make use of the new legal authority granted by the Peace Preservation Law to ferret out and suppress subversive ideologies.

By 1933, coerced "ideological conversions" (転向, tenkō) had become the main means of enforcing the Peace Preservation Law, rather than judicial punishment.

Terms for people suspected of socialist and communist sympathies were made harsher, and for the first time religious organizations were included within the purview of the Thought Police.

From 1925 through 1945, over 70,000 people were arrested under the provisions of the Peace Preservation Law, but only about 10% reached trial, and the death penalty was imposed on only two offenders, spy Richard Sorge and his informant, Hotsumi Ozaki.