A mentally incompetent person can generally enforce a contract only if:

A mentally incompetent person can generally enforce a contract only if they are deemed competent by a court. This is because the law recognizes that certain individuals may not have the capacity to understand the nature and consequences of their actions, particularly when it comes to entering contracts. When a court evaluates an individual's mental competency, it assesses their ability to comprehend and engage in contractual agreements. If the court finds the individual to be competent, they can enforce contracts as any other party would.

In many legal contexts, the other options do not provide the same level of assurance regarding a mentally incompetent person’s ability to enforce a contract. While the other party's agreement or the presence of a guardian's consent may offer some protection or support, they do not change the legal standing regarding competency. Contracts for necessities, while some jurisdictions might allow enforcement for essentials like food or shelter, still hinge on the recognition of the individual's competency. Therefore, the court's determination of competency is the most reliable condition under which a mentally incompetent person can enforce a contract.