10 U.S.C. § 950a

(a) Error of Law .— A finding or sentence of a military commission under this chapter may not be held incorrect on the ground of an error of law unless the error materially prejudices the substantial rights of the accused. (b) Lesser Included Offense .— Any reviewing authority with the power to approve or affirm a finding of guilty by a military commission under this chapter may approve or affirm, instead, so much of the finding as includes a lesser included offense.