The U.S. State Department has not revoked the passports of the dozen or so Americans who are fighting overseas for the Islamic State, a White House official told Congress on Tuesday.

Rep. Ron DeSantis, R-Fla., asked Ambassador Robert Bradtke during a House Foreign Affairs subcommittee hearing, "Has the State Department cancelled the passports of any U.S. citizens who have joined any terrorist groups in Syria and Iraq?"

"To my knowledge, the State Department has not cancelled any passports," Bradtke responded, according to CNS News. Bradtke is a senior adviser with the Bureau of Counterterrorism, and was called out of retirement to focus on foreign fighters.

"As Secretary Kerry said, he does have the authority to revoke passports," continued Bradtke. "And this is something we would only do in relatively rare and unique circumstances because of the importance for average Americans [to] have the freedom to travel."

"We would only do it also in consultations with law enforcement authorities. And we have not yet had any requests from law enforcement authorities to cancel the passports of ISIS or foreign fighters. So again, we have the authority; it is one tool; we do have other tools to use as well in this regard."

In October, FBI Director James Comey told CBS's "60 Minutes" that he is aware of a "dozen or so" Americans who are currently fighting amongst terrorists in Syria.

Unless their passport is revoked, Americans who have fought amongst Islamic State terrorists are "entitled to come back," Comey said.

"Ultimately, an American citizen, unless their passport's revoked, is entitled to come back. So, someone who's fought with ISIL, with an American passport wants to come back, we will track them very carefully."

Another administration official, Thomas Warrick, said that if someone who had been fighting with a terrorist group did somehow manage to return to the U.S., their information would be referred to the FBI, and "then it would be a matter for law enforcement."

But if an American foreign fighter did attempt to return home, their inclusion on a no-fly list would likely prevent them from getting very far, Warrick claimed.

"Where somebody has been identified as a foreign fighter fighting for ISIL in Syria...they're going to be in all likelihood on a no-fly list or another list of the U.S. government that is going to attract a great deal of attention before they're allowed to get on board an airplane for the United States," he said.