Is it permissible to dispose of the property of a mentally ill person against their will, under the pretext that their opinion is not to be taken into consideration due to their illness?

Psychological illnesses are of various types and degrees. The mere existence of a mental illness does not permit placing a person under interdiction. Rather, interdiction is permissible if the illness becomes problematic, prevents the individual from managing their wealth properly, and renders them akin to a spendthrift (safeeh). The ruling of interdiction does not apply except by the ruling of a judge or a qadi. Subsequently, a guardian (qayyım) is appointed over the interdicted person's wealth, obligated to preserve and grow it. The guardian is not permitted to dispose of the interdicted person's wealth except in ways that benefit them. They are not allowed to make donations or show favoritism. If they do so, they are liable for what they donated or favored. Therefore, the elder brother's disposal of his ill brother's wealth is not permissible, and the matter must be referred to the judge.