WASHINGTON -- President Donald Trump declared late Wednesday that he was designating the antifa movement a terrorist organization, amid a broader effort by his administration to threaten liberal protesters and donors to progressive groups after the killing of conservative activist Charlie Kirk.

Trump had made the same declaration in May 2020, but nothing came of it. And there are major factual and legal challenges to any government effort to formally designate antifa a terrorist group in any substantive way.

Here is a closer look.

What is antifa?

It is a diffuse and sometimes violent protest culture of far-left activists who want to stop the far right. The movement is associated with an aggressive form of protest its adherents call "direct action," which can sometimes cross the line into illegal or violent activity like breaking store windows or setting police cars on fire.

"'Antifa' is short for anti-fascist and is most often used to reference activists and protesters who support more direct methods of confronting the far right," said Jared Holt, a researcher of extremist movements at Open Measures, a company that monitors influence operations online. "Some who have self-labeled with the term have engaged in threatening or violent behaviors, but those individuals represent a small number of people who self-identify with the term."

Is antifa actually an organization?

No.

Antifa is a label for a political subculture or protest style. The phenomenon does not have a leader, an initiation process, membership rolls, a headquarters, a bank account or a centralized structure.

Cynthia Miller-Idriss, an American University professor who studies domestic extremism, said antifa was an idea that could mobilize people. She compared it to concepts or ideologies like "white supremacy" and "Islamist extremism," as distinguished from specific groups such as the Aryan Brotherhood or al-Qaida.

"There may be little groups organized around antifa in a neighborhood or community that meet up and share that stance, but it would be very hard to see that as connected in an organizational form that could be tackled," she said, adding, "There is no expert I've ever heard of who has identified antifa as an actual organization."

What did Trump say?

He announced the designation on his social media platform and threatened to investigate anyone funding antifa.

"I am pleased to inform our many U.S.A. Patriots that I am designating ANTIFA, A SICK, DANGEROUS, RADICAL LEFT DISASTER, AS A MAJOR TERRORIST ORGANIZATION," he wrote. "I will also be strongly recommending that those funding ANTIFA be thoroughly investigated in accordance with the highest legal standards and practices."

Can the U.S. designate domestic groups as terrorists?

No.

Federal law empowers the executive branch to deem overseas groups "foreign terrorist organizations." The law gives such groups a due process right to hearings to challenge the designation. If the designation stands, the status allows the government to freeze such groups' assets and makes it a crime to provide material support to them.

But there is no equivalent domestic terrorism law, noted Mary McCord, a former acting head of the Justice Department's national security division during the tail end of the Obama administration and opening months of the first Trump administration.

"Trump can declare whatever he wants to declare, but there is no legal authority to actually designate a domestic group as a terrorist organization even assuming that antifa is an organization and not just an ideology," she said. "That means his declaring this has no legal impact. Certainly, it does not trigger criminal terrorism charges, like providing material support to a foreign terrorist organization."

Would the Constitution allow this?

First Amendment protections for freedom of speech and association would probably bar any attempt by Congress to enact a statute allowing the government to designate domestic groups as terrorist organizations and make it a crime to help them, legal specialists say.

In a 2010 case in which the Supreme Court upheld the prosecution of a charity for steering funds to a designated foreign terrorist organization, Chief Justice John Roberts distinguished the matter from sending funds to a domestic organization.

Hypothetical attempts to criminalize support for designated terrorist groups under different circumstances might not "survive First Amendment scrutiny," he wrote, adding, "We also do not suggest that Congress could extend the same prohibition on material support at issue here to domestic organizations."

Because of First Amendment concerns, when the FBI has carried out what are effectively domestic terrorism investigations into neo-Nazi organizations like the Base and Atomwaffen Division, it has instead treated them as criminal enterprises.

What was the context of Trump's declaration?

Trump and his administration are using the killing of Kirk -- and criticism of Kirk from some liberals -- to threaten to use federal power to punish what it claims, without evidence, is a vast left-wing network that funds and incites violence. Democrats have warned that Trump appears to be using the killing as a pretext to suppress political dissent.

Among other things, Trump has also said the Justice Department would conduct a racketeering investigation into George Soros, the billionaire who funds civil-society and liberal causes, accusing him without evidence of paying people to riot. Brendan Carr, the Federal Communications Commission chair, threatened ABC over remarks by late-night host Jimmy Kimmel, and the network took him off the air.

Against that backdrop, Trump's declaration that he would designate antifa a terrorist organization was greeted with praise by various Republican lawmakers.

What happened last time?

Nothing -- but Trump is less constrained now.

In May 2020, as the Black Lives Matter protests swelled after the videotaped police killing of George Floyd in Minneapolis and some protests were marred by rioting, Trump declared on social media that the federal government "will be designating ANTIFA as a Terrorist Organization."

The first Trump administration did not follow through on his declaration. But that does not mean that the second Trump administration will not try to do so this time -- even if there is no clear legal or factual basis to justify such a declaration. Trump and his team have systematically sought to install loyalists in his second term who would not seek to constrain him.

For example, back in 2020, Trump wanted to use the military against protesters, but his administration did not follow through after his top aides resisted. But in June, after some protests against his immigration crackdown in Los Angeles turned violent, Trump sent federal troops into the streets of that city to suppress the demonstrations -- and then continued to use them for police functions for months, in a way a judge has ruled illegal. The administration has appealed that ruling.

Notably, the second Trump administration has already been pushing the limits of the president's terrorism designation powers by declaring various foreign criminal gangs and drug cartels to be foreign terrorist organizations, even though they are motivated by profit, not religion or ideology.

Can Trump designate antifa as a terrorist group? Here are the facts