Cornell University Law School states that the term "competence" applies to an individual who is legally "capable of entering into a binding contract, transferring assets, or participating in a legal proceeding." According to LGCSC Legal, different states have their own assessment procedures that they use to determine an individuals' mental competence and capacity and which rights are able to be removed from an individual who is classified as mentally incompetent.
According to Alec Buchanan, PhD MD, in his National Library of Medicine article "Mental capacity, legal competence and consent to treatment," when a patient refuses medical treatment, those wishes are required to be respected under U.K., U.S. and Canadian law unless the patient can be shown to be not legally competent.
Buchanan states that the mental capacity required for legal competence increases or decreases depending on the seriousness of what is at stake, and so legal competence is specific to the task at hand. Legal competence requires the mental capacities to "reason and deliberate, hold appropriate values and goals, appreciate one's circumstances, understand information one is given, and communicate a choice."
Buchanan explains that because laws recognize that mental capacity is a constant quality that can change over time and present to a greater or lesser extent, medical procedures that require consent over long periods of time often require repeated assessments to ensure that the legal mental capacity of a patient remains the same and that no legal rights are being withheld or mishandled.
Cornell University explains that there are legal standards through which those who are mentally ill can be forced to receive treatment against their will. Because involuntary commitment severely infringes on a person's right to be free from government restraint and the right to not be unnecessarily confined, statutes for involuntary commitment are subject to the due process clause of the 14th Amendment.