With reference to recent cases and new legislation, Peter Bartlett and Ralph Sandland analyse the legal structure and functions of the mental health system, and the problems of characterizing mental health law. The legal issues described contain implied premises as to what it is to be a citizen, what the role of the state is for the vulnerable, and what the relative roles of law and medicine are in the regulation of control and deviance. Mental health law is an area of considerable legal and social complexity, and the authors challenge readers to question the system and the policies that have been developed.