Let's start with the majority opinion.
The first inaccuracy seems to arise from imprecise use of language rather than a lack of understanding of the system. Justice Kennedy's opinion for the Court explains, "In exchange for his plea the convening authority referred respondent's case to a special court-martial, §819, which, at the time, could not impose a sentence greater than six months' confinement." Denedo, slip op. at 2. Of course, even before the National Defense Authorization Act for Fiscal Year 2000 increased the length of confinement that a special court-martial could adjudge, special courts-martial could (and often did) impose sentences greater than six months' confinement -- in a case with an enlisted accused, they could impose a sentence of six months' confinement, plus a bad-conduct discharge, plus forfeiture of 2/3 pay per month for 6 months, plus reduction to pay grade E-1.
Second, in discussing Clinton v. Goldsmith, the Denedo majority opinion states: "Following [Major Goldsmith's] conviction, Congress enacted a statute authorizing the President to drop convicted officers from the rolls of the Armed Forces." Denedo, slip op. at 7. Actually, authorization to drop convicted officers from the rolls existed long before Maj Goldsmith's conviction; in fact, section 10 of the UCMJ as enacted in 1950 provided that "the President may at any time drop from the rolls of any armed force any officer who has been absent without authority from his place of duty for a period of three months or more, or who, having been found guilty by the civil authorities of any offense, is finally sentenced to confinement in a Federal or State penitentiary or correctional institution." 81 P.L. 506, § 10; 64 Stat. 107, 146. What the National Defense Authorization Act for Fiscal Year 1996, 110 Stat. 325, actually did was expand the grounds for dropping an officer from the rolls to include confinement for at least six months resulting from a court-martial conviction.
Third, the Denedo majority opinion rather obviously mischaracterizes what happened in Clinton v. Goldsmith. The Denedo majority opinion states, "Goldsmith sought extraordinary relief as authorized by the All Writs Act to enjoin the President from removing him from the rolls. The AFCCA denied relief, but the CAAF granted it." Denedo, slip op. at 7. In fact, Maj Goldsmith never petitioned AFCCA to enjoin the President from dropping him from the rolls. It's strange that the Denedo majority would make this mistake, because Justice Souter's opinion for the Court in Clinton v. Goldsmith emphasizes this point:
Goldsmith did not immediately contest the proposal to drop him, but rather petitioned the Air Force Court of Criminal Appeals for extraordinary relief under the All Writs Act, 28 U.S.C. § 1651(a), to redress the unrelated alleged interruption of his HIV medication during his incarceration. The Court of Criminal Appeals ruled that it lacked jurisdiction to act, and it was in Goldsmith's appeal from that determination that he took the first steps to raise the issue now before us, an entirely new claim that the Air Force's action to drop him from the rolls was unconstitutional.526 U.S. 529, 532-33 (1999).
Fourth, the Denedo majority doesn't seem to understand the distinction between the court-martial and the convening authority. The majority quotes Article 67(c)'s language that CAAF has authority over "matters of law" connected to "the findings and sentence as approved by the convening authority . . . ." Denedo, slip op. at 10. Explaining how that provision is satisfied in this case, the majority opinion states, "Respondent's Sixth Amendment claim presents a 'matte[r] of law' with respect to the [guilty] findings . . . as approved by the [special court-martial] . . . ." Id. (all alterations except final ellipsis in original). So the Court substituted "as approved by the [special court-martial]" for "as approved by the convening authority." But, of course, it isn't the special court-martial that approves its own findings and sentence. Rather, it's the convening authority--in Denedo's case the Commanding Officer of USS JOHN F. KENNEDY--who approves the sentence (and who sometimes acts on the findings).
The dissent also got a couple of little things wrong. First, Chief Justice Roberts' dissenting opinion states, "The CCAs provide direct, record-based review of court-martial judgments, but they may only review cases referred by the judge advocate general, who in turn refers only those cases in which specific sentences are imposed. 10 U.S.C. §§866(b), (c)." Denedo dissent, slip op. at 3. But a Judge Advocate General doesn't refer only cases resulting in a specific sentence. Rather, a Judge Advocate General can -- and, as AFCCA's recent decision in United States v. Harvey demonstrates, sometimes does -- refer cases with lesser sentences to a CCA under the authority granted by Congress in Article 69(d)(1).
The other minor glitch in the dissent occurs in its discussion of DuBay hearings. The dissenting opinion states, "Instead, the CCAs will have to resort to the procedures invented by United States v. DuBay, 17 U.S.C.M.A. 147, 37 C.M.R. 411 (1967), under which a new convening authority will refer a case to a new court-martial, and task various military personnel who have no prior familiarity with the case to conduct an out-of-court evidentiary hearing on the merits of the petitioner's claim." Denedo dissent, slip op. at 10. First, of course, DuBay hearings aren't necessarily sent to a "new convening authority"; the case is often remanded to the same convening authority who convened the original court-martial. Nor is the case necessarily referred to a new court-martial. I can't think of a time when I've seen a new court-martial created to handle a DuBay hearing. Has anyone else? Finally, I have no idea what the dissent means by "an out-of-court evidentiary hearing." The whole point of a DuBay hearing is to have an in-court evidentiary hearing.
These errors are all minor; overall, the Court did a good job dealing with our rather idiosyncratic system. Still, it's striking how many even small errors are in a decision of an institution with the stature and brainpower of the Supreme Court.