This timely book investigates how AI systems can be designed to comply with overlapping EU regulatory frameworks, including those protecting personal data, the AI Act, and cybersecurity regulations. In order to guide this compliance, Bjørn Aslak Juliussen proposes a novel ‘proportionality by design’ framework. Chapters examine common methods used to build and maintain AI systems, focusing on machine learning operations. Juliussen assesses these as a methodology capable of integrating legal principles and legal requirements such as accuracy, transparency, and purpose limitation into AI systems. In line with the Charter of Fundamental Rights of the European Union, he maps technical and legal compliance requirements across key phases of the AI system lifecycle, highlighting the need for clearer definitions and standards within machine learning operations to support regulatory alignment. A vital resource for students and academics in European law, innovations and technology, and AI governance and regulation, Compliance by Design in AI Systems is also an essential read for policymakers and data protection professionals.