Is the addict a criminal or a patient? Should addicts be approached with coercive means or in such a way that his/her individual freedom is protected? This way of framing the problem of addiction opposes freedom and coercion, care and constraint, activity and subjugation. These dualisms have structured the French medical and legal debates until recently. At the beginning of the 1990s, however, the evident opposition between freedom and coercion was problematised. The critics tentatively designed a new form of substitution treatment. With methadone and other constraints, this treatment was a search for ‘generous constraint’, that is, for the conditions under which coercion might do a little more than oppress the user. Through a detailed description of several techniques of this experimental treatment, an original variation is added to the anthology of relations between care and coercion. Moreover, this contribution, inspired by ANT, seeks to participate in a criticism of the liberal definition of the human agent.