In Japan, the collection of electronic information in the area of criminal law enforcement foremost (103) falls within the responsibilities of the Prefectural Police (104), which in this regard is subject to various layers of oversight.
First, in all cases where electronic information is collected by compulsory means (search and seizure), the police has to obtain a prior court warrant (see recital 121). Therefore, the collection in those cases will be checked ex ante by a judge, based on a strict "adequate cause" standard.
While there is no ex-ante check by a judge in the case of requests for voluntary disclosure, business operators to whom such requests are addressed can object to them without risking any negative consequences (and will have to take into account the privacy impact of any disclosure). Moreover, according to Article 192(1) of the CCP, police officials shall always cooperate and coordinate their actions with the public prosecutor (and the Prefectural Public Safety Commission) (105). In turn, the public prosecutor may give the necessary general instructions setting forth standards for a fair investigation and/or issue specific orders with respect to an individual investigation (Article 193 of the CCP). Where such instructions and/or orders are not followed, the prosecution may file charges for disciplinary action (Article 194 of the CCP). Hence, the Prefectural Police operates under the supervision of the public prosecutor.
Second, according to Article 62 of the Constitution, each House of the Japanese parliament (the Diet) may conduct investigations in relation to the government, including with respect to the lawfulness of information collection by the police. To that end, it may demand the presence and testimony of witnesses, and/or the production of records. Those powers of inquiry are further specified in the Diet Law, in particular Chapter XII. In particular, Article 104 of the Diet Law provides that the Cabinet, public agencies and other parts of the government "must comply with the requests of a House or any of its Committees for the production of reports and records necessary for consideration of investigation." Refusal to comply is allowed only if the government provides a plausible reason found acceptable by the Diet, or upon issuance of a formal declaration that the production of the reports or records would be "gravely detrimental to the national interest" (106). In addition, Diet members may ask written questions to the Cabinet (Articles 74, 75 of the Diet Law), and in the past such "written inquiries" have also addressed the handling of personal information by the administration (107). The Diet's role in supervising the executive is supported by reporting obligations, for instance pursuant to Article 29 of the Wiretapping Act.
Third, also within the executive branch the Prefectural Police is subject to independent oversight. That includes in particular the Prefectural Public Safety Commissions established at prefectural level to ensure democratic administration and political neutrality of the police (108). These commissions are composed of members appointed by the Prefectural Governor with the consent of the Prefectural Assembly (from among citizens with no public servant position in the police in the five preceding years) and have a secure term of office (in particular only dismissal for good cause) (109). According to the information received, they are not subject to instructions, and thus can be considered as fully independent (110). As regards the tasks and powers of the Prefectural Public Safety Commissions, pursuant to Article 38(3) in conjunction with Articles 2 and 36(2) of the Police Law they are responsible for "the protection of [the] rights and freedom of an individual". To this effect, they are empowered to “supervise” (111) all investigatory activities of the Prefectural Police, including the collection of personal data. Notably, the commissions "may direct the [P]refectural [P]olice in detail or in a specific individual case of inspection of police personnel's misconduct, if necessary" (112). When the Chief of the Prefectural Police (113) receives such a direction or by him-/herself becomes aware of a possible case of misconduct (including the violation of laws or other neglect of duties), (s)he has to promptly inspect the case and report the inspection result to the Prefectural Public Safety Commission (Article 56(3) of the Police Law). Where the latter considers this necessary, it may also designate one of its members to review the status of implementation. The process continues until the Prefectural Public Safety Commission is satisfied that the incident has been appropriately addressed.
In addition, with respect to the correct application of the APPIHAO, the competent minister or agency head (e.g. the Commissioner General of the NPA) has enforcement authority, subject to the supervision by the Ministry of Internal Affairs and Communications (MIC). According to Article 49 APPIHAO, the MIC "may collect reports on the status of enforcement of this Act" from the heads of Administrative Organs (Minister). That oversight function is supported by input from MIC's 51 "comprehensive information centres" (one in each Prefecture throughout Japan) that each year handle thousands of inquiries from individuals (114) (which, in turn, may reveal possible violations of the law). Where it considers this necessary for ensuring compliance with the Act, MIC may request the submission of explanations and materials, and issue opinions, concerning the handling of personal information by the concerned Administrative Organ (Articles 50, 51 APPIHAO).