President Donald Trump and his administration are increasingly blaming antifa , a loosely organized anti-fascist group, for violence at protests across the country against police brutality and racism. The president tweeted Sunday that antifa will be labeled a terrorist group, and on Monday he vowed to use the military and the Justice Department to aggressively crack down on terrorist protesters.

The Justice Department, led by Attorney General William Barr , is following the presidents lead. Federal prosecutors are gearing up to use available laws, including one a federal judge recently declared unconstitutional, to crack down on violent demonstrations and seem poised to follow an aggressive prosecution model they used against even nonviolent protesters arrested during Trumps 2017 inauguration.

The violence instigated and carried out by Antifa and other similar groups in connection with the rioting is domestic terrorism and will be treated accordingly, Barr said Sunday.

One of Trumps prominent political allies, Rep. Matt Gaetz (R-Fla.), asked on Twitter whether , now that antifa is being considered a terrorist organization, the U.S. can hunt them down like we do those in the Middle East.

But the federal government cant just treat members of a domestic movement the way theyd treat al Qaeda because the president declares them terrorists via tweet , and there are a limited number of federal laws that apply to specific conduct during protests. Past federal efforts to prosecute alleged rioters have been tossed out by judges or lost at trial.

The fact that Trump and the Justice Department are devoting federal law enforcement resources to investigating antifa and publicly declaring the loose organization guilty before the investigation has taken place could have a chilling effect on protesters, distract from the racial justice message and, potentially, mire individuals in years-long court proceedings even if they werent involved in violence at all.

Barr who stood behind a police line near the White House on Monday evening as law enforcement prepared to violently clear the area for a presidential photo-op in front of a church said Sunday that federal law enforcement was working with 56 regional FBI Joint Terrorism Task Forces (JTTF) to identify criminal organizers and instigators as well as coordinate federal resources with state and local law enforcement.

Mary McCord, the former head of the Justice Departments national security division, told HuffPost that, although getting JTTFs to aid investigations was standard, it was unusual and troubling for Barr to suggest publicly that the violence is being perpetrated by anti-fascist activists without citing evidence.

Reporting from various protests around the country suggests outside groups, rather than local community members, have in some instances instigated destruction of property and violence, but the same reporting has suggested that some of this is being perpetrated by far-right extremist groups, McCord said. It is irresponsible to cast blame on any particular group or ideology when the investigations are just beginning.

Even so, McCord said that she believes Trump might indeed issue an executive order and emergency declaration that designates antifa as a domestic terrorist organization, though that has little practical effect. Domestic organizations, including those with extensive histories of terrorist activity, such as the Ku Klux Klan, are unlike designated foreign terrorist organizations protected by the First Amendment.

Besides the fact that Antifa is not a definable organization, any such designation would not trigger criminal penalties for providing material support or resources to a designated foreign terrorist organization because the material support statute by its terms only applies to foreign terrorist organizations, McCord said.

A Justice Department spokeswoman did not respond to a request for comment about Trumps call to designate antifa as a terrorist organization but wrote on Twitter that the Justice Department WILL be enforcing laws that make it a federal crime to cross state lines or to use interstate facilities to incite or participate in violent rioting.

Barr was on Trumps call with governors today as the president called state leaders weak for their response to unrest and told participants that he would activate Barr very strongly against rioters.

Barr told governors that there were several federal charges that could be brought, including charges against anyone who crossed state lines to participate in rioting and charging anyone who uses any interstate facility including telecommunications, vehicles, roads, whatever in connection with participating in or urging a riot.

There are a number of crimes that have been committed during the nationwide unrest that clearly have a federal nexus. The FBI is searching for gunmen who killed Dave Patrick Underwood , a contract security officer with the Federal Protection Service, and injured another security officer Friday outside a federal courthouse in Oakland, California. His death would be covered by a federal terrorism-related law that makes it a crime to kill or attempt to kill a federal employee. Rioters could face federal terrorism-related charges for malicious damage to federal property by means of fire or explosive, willful injury or depredation of any federal property, or malicious damage to a building or personal property used in interstate or foreign commerce.