Preventive outpatient commitment laws require people with mental illnesses to participate in mental health treatment before they meet the criteria for inpatient civil commitment -- clear and convincing evidence of mental illness and dangerousness to self or others. These laws apply to people who are chronically ill but not imminently dangerous. Most outpatient commitment laws do not require a judicial determination of incompetence, nor do they require a criminal charge or a criminal conviction. As such, outpatient commitment statutes unearth an old question on law, ethics, and the limits of prevention: under what circumstances can we impose substantial restraints on individual liberty because we believe a person is likely to harm himself or others before he actually has done so?Although most authors rest the moral justification for outpatient commitment on a mental impairment -- be it impaired insight, decisional-incapacity or incompetence to refuse treatment, this Article claims that government interventions into self-regarding harm and other-regarding harm require distinct moral justifications. When our primary concern is one of self-regarding harm, a court order to participate in outpatient treatment may be appropriate, but only for people with mental illnesses who are incompetent to make treatment decisions on their own. If, however, we are concerned about harm to others, a court order to participate in outpatient treatment may be appropriate, but only for people with mental illnesses who lack the moral capacities for criminal responsibility -- either because they are unlikely to appreciate the wrongfulness of their conduct or because they are unable to conform their conduct to the requirements of the law.