WASHINGTON — President Donald Trump blamed antifa activists for the violence at protests on police killings of black men, but antifa isn't an organization and targeting it is not easy.

A look about antifa and what it's not :

WHAT DOES ANTIFA MEAN ?

It is short for "anti-fascists," antifa is not a single organization but rather an umbrella term to far-left-leaning militant groups which confront or resist neo-Nazis and white supremacists at demonstrations.

There is no hierarchical form to antifa or universal set of stratigy that makes its existance immediately recognizable, though members tend to espouse revolutionary and anti-authoritarian views, said Mr.Mark Bray, a historian at Rutgers University and author of "Antifa: The Anti-Fascist Handbook."

"They do variouse things at variouse times in variouse ways, some of which there is evidence on them against the law. Other times there is not," Bray said.

Literature from the antifa movement motivate followers to monitor the activities of white supremacist groups, publicize the personal information of perceived enemies, improve self-defense training regimens and compel outside organizations to cancel any speakers or events with "a fascist bent," according to the2018 Congressional Research Service report.

People with antifa have been present for significant demonstrations and counter demonstrations for the last three years, sometimes including brawls and property desaster.

This groupe mobilized against a white supremacist marches in Charlottesville, Virginia, in August 2017 and have clashed many times with far-right groups in Portland, Oregon, including at a rally last summer that resulted in arrests and the seizure of shields, poles and other .

And we ask ourselves : WHAT ROLE IS ANTIFA PLAYING IN THESE DEMONSTRATIONS?

Trump and members of his goernment have removed antifa as being the doer for the violence at protests triggered by the killing of George Floyd, a black man died after a white Minneapolis police officer pushed on his knee into his neck for several minutes even after Floyd stopped moving and asking for air.

In a pair of statements for the weekend, Attorney General William Barr described "antifa-like tactics" by out-of-state agitators and said that antifa was instigating violence and engaging in "domestic terrorism" and would be dealt with accordingly as his saying.

White House press secretary Kayleigh McEnany said to the reporters Monday that antifa is a "huge element of this events," though deferred to the Justice Department on the question of how one could be identified as a member.

But it's not clear how huge its involvement is.

Bray said that although he thinks people with antifa are helping in the demonstrations, it is hard to know how big of a role they're doing since there is no membership uniform or calling card and since the movement doesnt have the numbers to mobilize nationwide in such a dramatic way.

"The radical left is too bigger than antifa, 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 TRUMP GOVERNMENT WANT TO DO ABOUT ANTIFA?

Trump said on Twitter Sunday, "The United States of America will be designating ANTIFA as a Terrorist Organization."

It's not the first time he's says that approach. Trump tweeted a similar statement last summer, joining some Republican lawers who called for antifa to be labeled as a terror organization following the skirmishes in Portland .

CAN THE ADMINISTRATION DO THAT?

Antifa is not a discrete or organized group, so it's not clear how the government could give it a designation.

After 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 involves Islamic extremist organizations and the Real Irish Republican Army, are based overseas more than in the U.S.

That labeling important for a variety of legal reasons, not least of which anyone in the United States who gives support to an organization on that list can face 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 are many periodic calls, particularly after mass shootings from white supremacists, to establish a domestic terrorism law, but none of them has passed.

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 see the acts of domestic and international terrorism.

But defining an act of terrorism is different than labeling an entire group as a terror organization.

"US law does the first. It doesn't permit the second," Geltzer tweeted after McEnany.

Even if antifa isn't a labeled terror organization, FBI Director Chris Wray said that it's on the radar of federal law enforcement. He made clear that while the FBI doesn't investigate on the basis of ideology, agents have pursued investigations across the US against people motivated to do events of violence "on kind of an antifa ideology."