A 1949 document unveiled by the Aichi Prefectural Government shows that the predecessor to the Justice Ministry tolerated "body restraint, anesthesia and deception" in "truly necessary and unavoidable" cases of the forced sterilization of people with disabilities under the now-defunct eugenics law.
The precursor to the Health, Labor and Welfare Ministry issued similar notifications to prefectural authorities the same year, according to a separate document unveiled by the Kyoto Prefectural Government.
The documents shed more light on the cases of historical human rights violations that have increasingly drawn the public's attention.
Japan has recently moved to investigate the damage caused under the eugenics law, in place between 1948 and 1996, which authorized the sterilization of people with visual and hearing impairments, intellectual disabilities, mental illness or hereditary disorders in order to prevent births of "inferior" offspring.
Around 25,000 people had their reproductive capacity removed under the law, including roughly 16,500 without consent, according to the Japan Federation of Bar Associations.
The government had been reluctant to carry out a survey on the matter but changed its stance after an intellectually disabled Miyagi Prefecture woman, now in her 60s, filed the first compensation claim regarding the law against the government in January, saying she was forcibly sterilized as a teenager.
The move prompted lawmakers to set up a nonpartisan group to study how to help the victims.