(1) A person may not vote at elections unless the person is: (a) registered as required by law; (b) 18 years of age or older; (c) a resident of the state of Montana and of the county in which the person offers to vote for at least 30 days, except as provided in 13-2-514; and (d) a citizen of the United States. (2) A person convicted of a felony does not have the right to vote while the person is serving a sentence in a penal institution. (3) A person adjudicated to be of unsound mind does not have the right to vote unless the person has been restored to capacity as provided by law.