The Legality of Donald Trump's Proposal to Try US Citizens by Military Commission

Republican presidential nominee Donald Trump made headlines once again yesterday by saying that he would be “fine” with trying American citizens accused of terrorism in military commissions at Guantanamo Bay. Trump stated that, “I want to make sure that if we have radical Islamic terrorists, we have a very safe place to keep them.” When asked by the Miami Herald whether he would seek to have U.S. citizens who are also terrorist suspects tried by commission at Guantanamo, Trump responded:

Well, I know that they want to try them in our regular court systems, and I don’t like that at all. I don’t like that at all. I would say they could be tried there, that would be fine.

Predictably, Trump’s comments have raised a new firestorm of criticism. And inquiring minds are calling out for Lawfare’s take—after all, the military commissions are a topic near and dear to our heart. So, at the risk of taking Trump’s whims on expanding the jurisdiction of military commissions too seriously, below is a very brief overview of the operative legal constraints.

Congress first authorized military commissions at Guantanamo in the Military Commissions Act of 2006. (The Act has since been revised under the Military Commissions Act of 2009.) The relevant section of the MCA reads as follows:

Sec. 948c. Persons subject to military commissions
Any alien unlawful enemy combatant is subject to trial by military commission under this chapter.

Since the MCA authorizes military commissions of “alien unlawful enemy combatant[s]” only, the trial by commission of a U.S. citizen—who is by definition not an alien—would not be authorized.

Therefore, as a matter of federal law, the trial of American citizens by military commission at Guantanamo Bay would be illegal. But Congress could always lift the statutory prohibition.

As a matter of constitutional law, the situation is more complicated. There actually is no clear constitutional jurisprudence expressly prohibiting the trial of American citizens by military commission. Across the span of a century, the Supreme Court has held both that the trial of a noncombatant U.S. citizen by military commission is unconstitutional when civilian courts are still available and operational (in Ex parte Milligan), and that the trial by military commission of a U.S. citizen who is also an unlawful enemy combatant is constitutional (in Ex parte Quirin).

In short, the statutory prohibition is clear and the constitutional ban less so. But for now, we doubt very much that the Office of Military Commissions is losing much sleep over the question.