"There's a disturbing pattern here, quite frankly, of not gathering intelligence when that opportunity exists," he said.
But Antonia Chayes, a professor at the Fletcher School of Law and Diplomacy at Tufts University in Medford, Mass., called the idea of holding Tsarnaev under that designation "hare-brained" and "ridiculous," saying it is generally reserved for those engaged in conflict on the battlefield who can't be extradited to the United States.
Although Tsarnaev will not be questioned as an enemy combatant, he also will not be read his Miranda rights before being interrogated by the HIG group to which Schumer referred.
Under an exception intended to preserve public safety, the Justice Department has decided that the surviving suspect will be questioned without first hearing that he has the right to a lawyer or to remain silent because of concerns of an imminent threat.
The American Civil Liberties Union has objected to such reasoning.
"Every criminal defendant is entitled to be read Miranda rights," the group wrote in a statement released Saturday. "The public safety exception should be read narrowly. It applies only when there is a continued threat to public safety and is not an open-ended exception to the Miranda rule.
"Additionally, every criminal defendant has a right to be brought before a judge and to have access to counsel. We must not waver from our tried-and-true justice system, even in the most difficult of times. Denial of rights is un-American and will only make it harder to obtain fair convictions."
A conviction could be put in jeopardy if DOJ waited an unreasonable amount of time to Mirandize the suspect, according to Chayes of Tufts University, but that would depend on the length of time, the judge and the facts of the case, many of which are unclear to the public.
"I think it really turns on the facts, and we don't know all the facts," she said. "Is there evidence of other participants of this that we have not been informed about? Are there rumors about it? Are there hints about it?
"If he's kept like that for, let's say, three weeks, you begin to wonder how in the world can they justify that. But if it's three days or even five days or something like that, then ?that sounds to me like reasonable."
Laura Dickinson, Oswald Symister Colclough Research Professor of Law at George Washington University in Washington, pointed out that Miranda rights still protect the suspect from incriminating himself before they are read by making anything he says at that point inadmissible in court.
"Here, it is unlikely the prosecution will ever need to introduce the defendant's statements; there will be so much other evidence against him," Dickinson wrote in an email to ABC News today.
"Accordingly, there is unlikely to be much impact from the lack of reading Miranda rights."