The scope of archive research and security investigations on public personnel to be appointed to important positions in terms of national security and public order was expanded after the state of emergency in 2016. Security investigations had started to be made for anyone to be appointed to public offi ce. In addition, with a new regulation introduced to the Law No. 4045 in 2018, the authorities conducting security investigations were allowed to access all kinds of information and documents in the hands of the administration, as well as court orders and other information subject to criminal procedures. However, the Constitutional Court annulled these regulations by fi nding them contrary to the Constitution in terms of protection of personal data due to the lack of suffi cient content and details to prevent the arbitrariness of the administration in Law No. 4045, which is the basis of security investigations. Although the Law No. 7315 on Security Investigation and Archive Research, which entered into force in April 2021, contains various regulations for the protection of personal data, it is controversial whether they are in suffi cient clarity and detail to prevent the arbitrariness of the administration. In this study, various legal problems regarding data protection in security investigations will be examined.