Mont. Code Ann. § 28-2-204
28-2-204 When person of unsound mind cannot disaffirm contract
28-2-204 . When person of unsound mind cannot disaffirm contract. A person of unsound mind cannot disaffirm a contract, otherwise valid, to pay the reasonable value of things necessary for the person's support or that of the person's family, entered into by the person when not under the care of a parent or guardian able to provide for the person or the person's family.