The United Nations Convention on the Rights of Persons with Disabilities (UNCRPD) has often been cited as the basis for the abolition of involuntary hospitalization for persons with mental illness. Although the UNCRPD itself does not refer explicitly to the abolition of involuntary hospitalization, the General Comment prohibited all compulsory admission without adequate explanation. While the disability status alone may not justify the denial of legal capacity, the existence of impaired decision-making ability can raise issues regarding whether involuntary admission can be justified in the best interest of persons with mental illness. The General Comment, however, argues that involuntary admission does not comply with the CRPD which prohibits discrimination on the basis of disabilities. This statement defies logic since the issue is whether the existence of impaired decision-making ability may be an exceptional case. It is also against the principles of beneficence to withhold treatment for persons with mental illness just for self-determination when poor outcomes are anticipated if left untreated. The concept of supported decision making suggested by the General Comment is also ambiguous, and not clearly distinguishable from substitute decision making. Another reason for the prohibition of involuntary admission relates to doubt concerning the accuracy of assessment of mental capacity, which implies adequate assessment may justify involuntary admission. In practice, it is not always complicated to assess mental capacity in order to make treatment-related decisions. The third reason concerns the argument that psychiatric treatments lack empirical evidence concerning effectiveness. Scientific evidence supporting the effectiveness of psychiatric treatment is abundant. The rights of persons with mental illness are important ethical issues. However, it is doubtful whether the blanket prohibition of compulsory admission is appropriate and ethical. Critical review of the UNCRPD and the General Comment is urgent for timely treatment and for the well-being of persons with mental illness.