What antifa is — and what it isn't.
Donald Trump has blamed antifa activists for violence at protests over police killings of black people, but antifa isn't an organization and targeting it isn't so simple.
A look at what antifa is and is not:
What is antifa?
Short for "anti-fascists," antifa is not a single organization but rather an umbrella term for far-left-leaning militant groups that confront or resist neo-Nazis and white supremacists at demonstrations.
There is no hierarchical structure to antifa or universal set of tactics that makes its presence immediately recognizable, though members tend to espouse revolutionary and anti-authoritarian views, said Mark Bray, a historian at Rutgers University and author of "Antifa: The Anti-Fascist Handbook."
"They do different things at different times in different ways, some of which there is evidence of them breaking the law. Other times there is not," Bray said.
Literature from the antifa movement encourages followers to pursue lawful protest activity as well as more confrontational acts, according to a 2018 Congressional Research Service report.
The literature suggests that followers monitor the activities of white supremacist groups, publicize online the personal information of perceived enemies, develop self-defense training regimens and compel outside organizations to cancel any speakers or events with "a fascist bent," the report said.
People associated with antifa have been present for significant demonstrations and counter-demonstrations over the last three years, sometimes involving brawls and property damage.
They mobilized against a white supremacist march in Charlottesville, Virginia, in August 2017 and have clashed repeatedly with far-right groups in Portland, Oregon, including at a protest and counter-demonstration last summer that resulted in arrests and the seizure of shields, poles and other weapons.
What role is antifa playing in these demonstrations?
Trump and members of his administration have singled out antifa as being responsible for the violence at protests triggered by the death of George Floyd, a black man killed by a white Minneapolis police officer who pressed his knee into Floyd's neck for several minutes even after Floyd stopped moving and pleading for air.
In a pair of statements over the weekend, Attorney General William Barr described "antifa-like tactics" by out-of-state agitators and said antifa was instigating violence and engaging in "domestic terrorism" and would be dealt with accordingly.
At a White House appearance Monday, Trump blamed antifa by name for the violence, along with violent mobs, arsonists and looters.
White House press secretary Kayleigh McEnany told reporters earlier in the day that antifa is a "big element of this protest," though she deferred to the Justice Department on the question of how one could be identified as a member.
But it's unclear how big its involvement is.
Bray said that although he believes people associated with antifa are participating in the demonstrations, it is difficult to establish how big of a role they're playing since there is no official roster of members and since the movement lacks the numbers to mobilize nationwide in such a dramatic, forceful way.
"The radical left is much bigger than — much, much bigger — and the number of people who are participating in the property destruction are much, much bigger than the radical left," Bray said.
Others have seen evidence of right-wing extremists.
What does the Trump administration want to do about antifa?
Trump tweeted Sunday, "The United States of America will be designating ANTIFA as a Terrorist Organization."
It's not the first time he's endorsed that approach. Trump expressed a similar sentiment last summer, joining some Republican lawmakers in calling for antifa to be designated as a terror organization after the skirmishes in Portland.
Can the administration do that?
For one thing, antifa is not a discrete or centralized group, so it's unclear how the government could give it a designation.
Beyond that, though, antifa is a domestic entity and, as such, not a candidate for inclusion on the State Department's list of foreign terror organizations. Those groups, which include Islamic extremist organizations and the Real Irish Republican Army, are based overseas rather than in the United States.-
That designation matters for a variety of legal reasons, not least of which anyone in the United States who lends material support to an organization on that list is subject to terrorism-related charges.
But "there is not a domestic equivalent," said Joshua Geltzer, a former senior counterterrorism official in the Obama White House and founding executive director at the Institute for Constitutional Advocacy and Protection at the Georgetown University Law Center.
There have been periodic calls, particularly after mass shootings by white supremacists, to establish a domestic terrorism law. But no singular domestic terrorism statute now exists.
Asked Monday what legal authority the president would have for labeling antifa a terror organization, McEnany pointed to the existing statute under the U.S. criminal code that defines acts of domestic and international terrorism.
But defining an act of terrorism is different than designating an entire U.S. group as a terror organization.
"US law does the 1st. It doesn't permit the 2nd," Geltzer tweeted after McEnany's remarks.
Even if antifa is not a designated terror organization, FBI Director Chris Wray has made clear that it's on the radar of federal law enforcement.
He has said that while the FBI does not investigate on the basis of ideology, agents have pursued investigations across the country against people motivated to commit crimes and acts of violence "on kind of an antifa ideology."