This chapter focuses on aspects of mental health law that are of particular relevance to psychiatrists working in general hospitals. The law is described as it stands in England and Wales on 1 August 2021, where the Mental Health Act (MHA) 1983 (amended in 2007) regulates the treatment of people with mental disorders and the Mental Capacity Act 2005 is intended to empower and protect people who lack the capacity to make decisions. Many countries have similar arrangements for mental health, particularly those in common law jurisdictions such as the United States, Canada, Australia, and New Zealand. Mental capacity law is more diverse across jurisdictions. A few jurisdictions, for instance Northern Ireland, have introduced legislation that fuses mental health and mental capacity, although it has not yet been implemented.