Protection against the unlawful deprivation of life and liberty, assured to persons with disabilities in the United Nations Convention on the Rights of Persons with Disability, is a negative freedom, unrealisable unless the right-bearer has the ability to realise such a freedom. This is rooted in the proposition that we cannot be considered free to do that which we are una- ble to do. Law’s recognition of ability to transact freely with the world is by way of the legal construct of capacity. Forced intervention and institution- alisation of persons with mental illness denies rational agency to persons with mental illnesses on an assessment of lack of capacity. The legal insti- tution of ‘guardians’ and other substituted decision-makers further aggra- vate this denial of capacity of persons with mental illness by providing for a denial of agency. This paper argues that the universalist model of legal capacity requires law-makers to embrace a paradigm shift, from viewing ability as central to the human condition (and consequently to ‘capacity’) to viewing ‘disability’ as central to the human condition. This would entail the recognition of the fact that all human beings are in some sense disa- bled ̧ thus widening the range of ‘normal’. This paradigm would only allow function-specific capacity assessment to be undertaken so as not to render capacity a status by the tag ‘mentally ill’. The paper also demonstrates the fallacy in the grounds employed to justify the use of force against persons with mental illness to further strengthen the case in favour of abolition of the use of forced medical intervention for persons with mental illness.