But so far, that does not include revoking the passports of U.S. citizens who have traveled to Syria to fight with ISIS.
"Has the State Department cancelled the passports of any U.S. citizens who have joined any terrorist groups in Syria and Iraq?" Rep. Ron DeSantis (R-Fla.) asked Ambassador Robert Bradtke on Tuesday at a hearing of a House Foreign Affairs subcommittee.
"To my knowledge, the State Department has not cancelled any passports," responded Bradtke, a senior adviser with the State Department's Bureau of Counterterrorism who was called out of retirement to focus on foreign fighters.
"As Secretary Kerry said, he does have the authority to revoke passports. 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," Bradtke said.
"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."
A second government official told lawmakers that the no-fly list is one of those other tools:
"Congressman, if we have indications that someone on the no-fly list is trying to fly back to the United States, we would deny them boarding," said Thomas Warrick, a deputy assistant secretary for counter-terrorism policy at the Department of Homeland Security.
"If someone shows up in the United States and there's indications that that person has been a foreign fighter in Syria, it would be referred to the FBI, and then it would be a matter for law enforcement," Warrick explained.
"We would have the ability at the border to ask any questions that were necessary and appropriate; we would have the ability and the authority to inspect their luggage, inspect their personal possessions, in order to determine whether they were or were not a foreign fighter who had been fighting with ISIL. Anything like this, I can assure you, is taken extremely seriously."
Later in the hearing, Warrick was asked what would happen if an Irish national, for example, tried to come to the U.S. after fighting with terrorists in Syria.
"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."
But Warrick admitted that the no-fly list can't guarantee that foreign fighters will be kept out of this country:
"Well, they wouldn't be able to fly here," he said. "The no-fly list obviously doesn't apply to other modes of transportation. However, I can assure you that there are equal or equivalent measures in place so that somebody on the no-fly list is almost certainly not going to be allowed entry into the United States, if they come by cruise ship or if they fly to Canada, for example...and they were to try, let's say, to come across the U.S.-Canadian border."
No one mentioned the U.S.-Mexico border, which was overwhelmed by an influx of people from Central America just a few months ago.
Warrick put the number of U.S. citizens fighting with ISIS/ISIL at "greater than a hundred," and he said some of those returning fighters have been arrested on arrival in this country. He did not say how many have been arrested, but when it happens, he said the returning fighters move from DHS purview to FBI purview.
Two Democrats on the subcommittee asked why the State Department has not hired its own expert on Islamic law.
"It is incredibly important that we get Islamic scholars, experts and jurists to issue rulings adverse to ISIS and favorable to the United States," said Rep. Brad Sherman (D-Calif.).
"It is about time that the State Department hire its first Islamic legal expert to work full time on that -- maybe a couple (of experts). And it is time that at least somebody be hired at the State Department, not because they went to a fancy American school or because they did well on the foreign service exam."
Sherman said he's been told that the State Department is relying on outsiders to provide expertise on Islamic law and issue statements that are favorable to the United States.
Rep. Gerald Connolly (D-Va.) said the Middle East is "unraveling," posing "a threat to us and the West."
"As the United States moves forward, it just seems that the State Department needs to be promoting leadership from within that has particular focus on this region, since that's what we're dealing with...I do think Mr. Sherman has a point, that longer term, the United States has got to get serious about this region and expertise in this region if we're going to address the challenges we face."
FBI Director: Americans Fighting With ISIS 'Entitled' to Come Back (Oct. 6, 2014)
British PM Plans to Seize Passports, Block Returning Jihadists (Sept. 1, 2014)
Mark Levin: Americans Joining ISIS Relinquish Their U.S. Citizenship (Sept. 4, 2014)