This comparative scoping review charts and compares current and emerging issues for mental health social workers involved in the use of compulsory mental health legislation in the UK and Ireland. It acknowledges a dearth of research evidence in this key area of social work practice and an urgent need to critically examine the use of such compulsory intervention given the significant human rights implications of forced detention and medical treatment. A case study approach is used in the paper with specific focus on the role that mental health social workers play in the delivery of community based compulsory treatment orders (CTOs) in three UK jurisdictions (England, Wales and Scotland) and two where, at present they are not used, nor are planned to be used (Northern Ireland and the Republic of Ireland). The paper starts by offering an historical overview of the mandated and other roles of mental health social workers in the UK and Ireland with particular attention to the shifts in policy and law created by the processes of devolution that have occurred in the last few decades. This discussion draws out distinctions between jurisdictions, but notes the common policy and legal imperatives that involve social workers in decision-making in relation to CTOs, and the use of compulsory measures more broadly. Analysis is provided in terms of comparative themes, including the rationale for CTOs, legal thresholds, service user rights and trends in the use of CTOs and equivalent statutory measures. Attention is paid to the roles social workers undertake, both in terms of formal decision-making regarding applications for CTOs and post-hoc care and monitoring. This is compared with the social work role in the two jurisdictions without CTOs: Northern Ireland and the Republic of Ireland. A discussion then takes place about the ethical and practice dilemmas that social workers experience in these contexts, including inherent tensions between the potentially coercive nature of CTOs and social work’s espoused commitment to human rights and social justice, set against the paradigmatic shift in thinking about the legality of compulsion reflected in the United Nations Convention on the Rights of Persons with Disabilities. The paper considers the extent to which social workers can bring a social perspective to counter prevailing medical discourses in framing and responding to mental distress in statutory settings and to uphold citizens’ broader social and cultural needs in the context of welfare austerity. It concludes with an appeal for future critical analyses of the mental health role when such compulsory laws are being applied.