Name: Regulations for Enforcement of the Radio Act
Publication date: 1950
Link: http://www.tele.soumu.go.jp/j/sys/ele/medical/system/index.htm 
Notes:  Article 14.2 (Limit of Specific Absorption Rate to human exposure)

Name: Ordinance regulating radio equipment
Publication date: 1950
Link: http://www.tele.soumu.go.jp/j/sys/ele/medical/system/index.htm 
Notes:  Article 21.3 (Safety facility about radio wave strength)

Name: Radio Protection Guidelines for Human Exposure to EMF 
Publication date: 1990 (revised 1997, 2011, 2015)
Link: http://www.tele.soumu.go.jp/j/sys/ele/medical/protect/index.htm 
Notes: In general, guidelines are voluntary, however, the Ministry of Internal Affairs and Communications (MIC) partly legislated Radio Protection Guidelines for Human Exposure to EMF as mandatory standards in 1999 (Mandatory for safety facility about radio wave strength, etc).