(1) If the convening authority disapproves the findings and sentence of a court-martial, he or she may, except where there is lack of sufficient evidence in the record to support the findings, order a rehearing. In such a case, he or she shall state the reasons for disapproval. If he or she disapproves the findings and sentence and does not order a rehearing, he or she shall dismiss the charges.
(2) Each rehearing shall take place before a court-martial whose composition shall not include any member or military judge of the court-martial which first heard the case. Upon a rehearing, the accused may not be tried for any offense of which he or she was found not guilty by the first court-martial, and no sentence in excess of or more severe than the original sentence may be imposed unless the sentence is based upon a finding of guilty of an offense considered upon the merits in the original proceedings or unless the sentence prescribed for the offense is mandatory.