Sentence:  Tribunals were set up as watchdogs in cases of compulsory detention (<WSD>sectioning</WSD>). ... Informal patients, however, could be <WSD>sectioned</WSD>, and this was often a fear of patients once they were in hospital. 
Meaning of the word marked with <WSD> tags:  To commit (a person, to a hospital, with or without their consent), as for mental health reasons. (So called after various sections of legal acts regarding mental health.)