The book addresses two key aspects. Firstly, it explores how data protection law, such as the General Data Protection Regulation (GDPR), works as a legal basis for technical standards. To identify standardization areas in data protection, the book proposes an analytical framework of standards for legal compliance, for beneficiaries, and meta-rules. Secondly, the book examines how procedural legitimacy issues, such as questions of transparency, representation, and accessibility, frame and limit the suitability of standardization to complement public law, especially law that protects fundamental rights, including the right to protection of personal data. Ultimately, it concludes by providing a comprehensive account of how a private regulation instrument may complement public law in pursuing its goals and where limits and conditions for such a role should be drawn.