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.

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 to ex officio oversight, individuals also have several possibilities for obtaining individual redress, both through independent authorities (such as the Prefectural Public Safety Commissions or the PPC) and the Japanese courts.

In addition, Article 79 of the Police Law guarantees individuals who have concerns with respect to the "execution of duties" by police personnel the right to lodge a complaint with the (competent) independent Prefectural Public Safety Commission. The Commission will "faithfully" handle such complaints in accordance with laws and local ordinances and shall notify the complainant in writing of the results. Based on its authority to supervise and "direct" the Prefectural Police with respect to "personnel's misconduct" (Articles 38(3), 43-2(1) of the Police Law), it may request the Prefectural Police to investigate the facts, take appropriate measures based on the outcome of this investigation and report on the results. If it considers that the investigation carried out by the Police has not been adequate, the Commission may also provide instructions on the handling of the complaint.

In order to facilitate complaint handling, the NPA has issued a "Notice" to the Police and Prefectural Public Safety Commissions on the proper handling of complaints regarding the execution of duties by police officers. In this document, the NPA stipulates standards for the interpretation and implementation of Article 79 of the Police Law. Among others, it requires the Prefectural Police to establish a "system for handling complaints" and to handle and report all complaints to the competent Prefectural Public Safety Commission "promptly". The Notice defines complaints as claims seeking correction "for any specific disadvantage that has been inflicted as the result of an illegal or inappropriate behaviour" (115) or "failure to take a necessary action, by a police officer in his/her execution of duty" (116), as well as any "grievance/discontent about inappropriate mode of duty execution by a police officer". The material scope of a complaint is thus broadly defined, covering any claim of unlawful collection of data, and the complainant does not have to demonstrate any harm suffered as a result of a police officer’s actions. Importantly, the Notice stipulates that foreigners (among others) shall be provided with assistance in formulating a complaint. Following a complaint, the Prefectural Public Safety Commissions are required to ensure that the Prefectural Police examines the facts, implements measures "according to the result of the examination" and reports on the results. Where the Commission considers the examination to be insufficient, it shall issue an instruction on the handling of the complaint, which the Prefectual Police is required to follow. Based on the reports received and the measures taken, the Commission notifies the individual indicating, among others, the measures taken to address the complaint. The NPA Notice stresses that complaints should be handled in a "sincere manner" and that the result should be notified "within the scope of time […] deemed appropriate in the light of the social norms and common sense".

As for the Prefectural Police, its responsibilities and duties include the "maintenance of public safety and order" (Article 35(2) in conjunction with Article 2(1) of the Police Law). Within this scope of jurisdiction, the police may collect information, but only on a voluntary basis without legal force. Moreover, the activities of the police shall be "strictly limited" to what is necessary to perform its duties. Moreover, it shall act in an "impartial, nonpartisan, unprejudiced and fair" manner and never abuse its powers "in any way such as to interfere with the rights and liberties of an individual guaranteed in the Constitution of Japan" (Article 2 of the Police Law).

As regards the Prefectural Police, oversight is ensured by the independent Prefectural Public Safety Commissions, as explained in recital 135 with respect to criminal law enforcement.