Section 29B.64 - Rehearings1. If the convening authority disapproves the findings and sentence of a court-martial the convening authority may, except where there is lack of sufficient evidence in the record to support the findings, order a rehearing. In such case the convening authority shall state the reasons for disapproval. If the convening authority disapproves the findings and sentence and does not order a rehearing, the convening authority 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 the accused 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.C66, 71, 73, 75, 77, 79, 81, § 29B.64