(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 composed of members not members 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 not considered upon the merits in the original proceedings, or unless the sentence prescribed for the offense is mandatory.