That’s the proposal Benjamin Wittes makes in today’s Washington Post. Wittes says that by splitting the legal baby, by “charging the 9/11 case in both military commissions and federal court,” the Obama administration can satisfy political considerations on both sides of the aisle.

This is a path fraught with legal issues. The constitutional bar against double jeopardy would prevent a trial in one forum and re-trial in the other for the same actions. Wittes spells out his proposal in greater detail in this post at the Lawfare blog, and he acknowledges this risk. The same sovereign cannot try someone twice for the same crime and Wittes acknowledges that the “John Allen Muhammed Model,” named after one of the Beltway snipers, used the separate sovereigns doctrine in ways that do not apply to Guantanamo. The Beltway snipers were liable for separate crimes in Maryland and Virginia in a way that does not translate directly to the 9/11 conspirators.

Wittes recognizes these legal issues and proposes that federal prosecutors and military commissions prosecutors clearly separate the crimes they respectively charge.

I’d go further. The clearest way to make this work is not to “charg[e] the 9/11 case in both military commissions and federal court.” This proposal only works if you charge pre‑9/​11 conduct in an Article III court and the 9/11 attacks in a military commission.

The Double Jeopardy Clause of the Fifth Amendment would prevent “charging the 9/11 case in both military commissions and federal court.” Federal prosecutors charged Khalid Sheikh Mohammed well before 9/11 for his participation in the Bojinka Plot, a plan to blow up airliners over the Pacific Ocean. To the extent that he and other 9/11 co-conspirators can be charged with crimes related to Bojinka or other pre‑9/​11 attacks, this would pass constitutional muster. Otherwise, this is a not an advisable course of action.

Where Double Jeopardy is a concern, the broad sweep of Material Support of Terrorism (MST) charges works against the government, not for it. If an MST charge is used in federal court in anything 9/11-related, the defendants have an excellent case that it bars any charges related to that attack in a military commission and vice versa. MST charges don’t even belong in a military commission, as Assistant Attorney General David Kris warned Congress before it revised the commissions with the Military Commissions Act of 2009. So if you’ve got MST on your mind, best to keep it in a civilian court. The Court of Military Commissions Review is getting ready to weigh the validity of MST in the commissions in the case of Ali al Bahlul, so stay tuned.

The Double Jeopardy bar in prosecuting before a military commission and then in a civilian court is also grounded in first principles. When Benedict Arnold betrayed General Washington and the fortifications at West Point, he escaped. His co-conspirators did not. British Major John André was tried and hanged by a military commission. Joshua Hett Smith, a citizen of New York and citizen of what would become the United States, was likewise tried by a panel of military officers. The panel found insufficient evidence to convict him. The prosecution failed to establish that he knew the true object of André’s meeting with Arnold, and might have reasonably believed that he was ferrying a British officer to negotiations with an American officer without knowledge of Arnold’s betrayal. When Smith transferred to a local jail, the civilian grand jury found that he could not be tried for treason for the actions that previously subjected him to a military trial; his protection from Double Jeopardy stood firm.

Keep in mind, I’m not endorsing Wittes’ plan. Wittes has a lot of “creative” ideas that I think are destructive of the liberty we’re trying to protect. He says in his book, Law and the Long War, that the “psychological Rubicon” of preventive detention is something “we simply need to cross.” Count me opposed, as I said in this post. But it’s worth noting that, before anyone gets too excited about a bipartisan compromise, there are serious issues with two sets of trials for KSM and the rest of the 9/11 co-conspirators.