In the wake of the horrific Boston Marathon bombings, certain Republican lawmakers—including Senators Kelly Ayotte, Lindsey Graham, and John McCain—were quick to call for the surviving suspect Dzhokhar Tsarnaev, an American citizen, to be treated as an “enemy combatant.” They have continued to beat this drum, most recently in a Boston Globe op-ed following Tsarnaev’s arraignment on criminal charges. The senators are wrong—dangerously so—on both the law and the practical ramifications of the “enemy combatant” designation.

The 2001 Authorization for Use of Military Force (AUMF), as supplemented by the National Defense Authorization Act (NDAA), provides the legal authority under which the executive branch targets, detains, and interrogates combatants. Courts have interpreted the AUMF to permit the detention of anyone who is part of al Qaeda, the Taliban, or “associated forces,” as well as anyone who “substantially supports” these groups (for instance, through the provision of materiel or manpower). As broad as this interpretation is, it does not encompass any Muslim who does harm to U.S. persons or interests, anywhere in the world, simply because he is inspired by—or sympathetic to—al Qaeda’s rhetoric. There must be a sufficiently close tie to an organized armed group with whom the United States is at war.

In the case of Tsarnaev, the relevant evidence that the senators cite in their op-ed consists of online postings indicating that his now-dead brother Tamerlan was a “follower of Al Qaeda–linked extremists” and a Russian intelligence report indicating that Tamerlan “may have met with a suspected militant” in Dagestan or Chechnya. Note the careful use of the word “militant”: there is no mention of al Qaeda or the Taliban. If a Guantánamo prisoner challenged his detention through a habeas corpus petition and the government’s response cited only these pieces of evidence, the judge would readily grant the detainee’s petition. These facts are plainly insufficient to justify indefinite detention as an enemy combatant.

The lawmakers appear to realize this. Rather than arguing that Tsarnaev is affiliated with al Qaeda, they argue that there is a “potential affiliation” and that he should be held and interrogated at length “to determine whether he had ties to foreign terrorist organizations” or, alternatively, “whether the brothers had acted alone.” In other words, Tsarnaev should be held as an enemy combatant in order to determine whether he is an enemy combatant. This argument should be beneath a senator such as Graham who routinely holds himself out as an expert in the law of war. In order to hold someone as an enemy combatant, the government must already have a sufficient factual basis—such as reliable intelligence reports or the fact that the individual was engaged in combat in an active war zone—to support the designation.

Then there’s that pesky matter of domestic law, including our Constitution. By statute, express legislative authorization is required to detain a U.S. citizen or to employ military forces for domestic law-enforcement purposes. Neither the AUMF nor the NDAA expressly authorizes the military detention of U.S. citizens. The Supreme Court has interpreted the AUMF to allow such detention, but the Court’s holding was limited to detainees captured while engaged in armed conflict in Afghanistan. Scholars have argued convincingly that detaining a U.S. citizen in the United States for conduct that occurred on American soil would violate the Constitution’s strong presumption against military involvement in domestic affairs.

Why are Ayotte, Graham, and McCain so intent on contorting the law? They argue that designating Tsarnaev an enemy combatant would have allowed the government to interrogate him without a lawyer for longer than the sixteen hours that he was questioned before being read his Miranda rights. But the government could have done this anyway, although it wisely chose not to. The Constitution doesn’t require the government to read non-combatants their rights; it simply prevents the use of any non-Mirandized statements in court. As the senators themselves acknowledge, “The only reason to quickly read a suspect his Miranda rights is to ensure his confessions can then be used in court against him.”

Of course, while the government had more leeway than it chose to take, it could not have continued to hold and interrogate Tsarnaev indefinitely without bringing charges. Ayotte, Graham, and McCain tacitly assume that useful intelligence gathering ceases at the point a suspect is brought within the criminal justice system. The evidence shows otherwise. The bargaining power that the government holds when pursuing a viable criminal prosecution can be a powerful tool for securing information. Defendants charged with terrorism have provided useful intelligence in numerous cases—often after being advised by their lawyers to cooperate.

One might still posit some practical advantage to the enemy combatant approach if the senators were seeking to have Tsarnaev tried by military commission or detained indefinitely without charge. However, the law does not permit U.S. citizens to be tried by military commission, and Ayotte, Graham, and McCain are not advocating that this law be changed or that Tsarnaev be held in indefinite detention. Recognizing that either recommendation would raise sticky legal and political problems, they support prosecution in federal court, blithely disregarding their own longstanding opposition to using civilian courts to try enemy combatants.

The idea of deeming Tsarnaev an enemy combatant is not simply without legal basis or practical advantage. It is also dangerous. The executive branch maintains that it has the legal right, under at least some circumstances, to unilaterally execute U.S. citizens whom it considers enemy combatants. It has not publicly identified the outer limits, if any, of that authority, and the courts have refused to weigh in on the issue. Accordingly, if we accept the idea that any American who has potential, unconfirmed ties to al Qaeda may thereby be presumed an enemy combatant, we are embracing the notion that he also may be killed, subject to rules that only the government knows.

War should never be waged so irresponsibly. A central and inviolable tenet of the law of war is the principle of distinction: the requirement that warring parties distinguish at all times between combatants and civilians. That principle extends a degree of protection even to those civilians who are accused of the most depraved criminal acts, including terrorism. We undermine the moral authority of our military operations when we play so fast and loose with categories such as enemy combatant. There is no short-term political gain that is worth this cost.