Donald Trump accused the "Antifa" movement of having fomented violence in the United States since the death of an American black man, George Floyd, at the hands of the police, assuring that the "radical" militants of the far left would be placed on the list of terrorist entities, such as the Islamic State or Al Qaeda groups.
But this promise could remain a dead letter as this informal network is far from being structured and because there is no anti-terrorist law for American groups.
Who are the Antifa?
The term "Antifa", a contraction of Antifascist Action, comes from Italian and then German socialist groups which tried to resist the rise of Benito Mussolini and Adolf Hitler in the 1920s and 1930s.
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Activists in the United States campaign mainly on social justice issues, such as minority rights.
"We believe in and fight for a world without fascism, racism, sexism, homo / transphobia, anti-Semitism, Islamophobia or hatred," said Antifa group from New York on Monday on its Twitter account.
But their main objective is the struggle against neo-Nazi movements, nationalist groups and white supremacists. One of the oldest, the Portland Rose City Antifa, stood out by canceling a neo-Nazi music festival in 2007.
Their tactics mainly include the organization of counter-demonstrations. But since the election of Donald Trump in 2016, after a fierce anti-immigrant campaign that released the speech of the radical far right, the Antifa have moved on to sometimes violent direct confrontations.
In January 2017, on the sidelines of the Republican president's inauguration ceremony, militants dressed in black and masked had protested violently in Washington, breaking windows. In August, they participated in the scuffles that punctuated a rally of ultra-right organizations in Charlottesville (Virginia) during which an anti-racist activist was killed.
The two camps also compete regularly, notably in Portland, New York and Berkeley, stronghold of leftist students in California.
But the Antifa are not a national organization and operate primarily as local "collectives," according to the Research Center of the United States Congress.
He describes them as a “decentralized movement, made up of independent and radical individuals and groups”. They are mostly non-violent, and some activists "are ready to commit crimes to promote their ideas".
Do the Antifa organize the violence? -
Apart from Trump and his close advisers, no politician has blamed the violence on the Antifa alone.
"Several national terrorist groups, far left and far right, are planning and committing acts of violence and looting," said Republican Marco Rubio, chairman of the Senate Intelligence Committee, on Sunday.
In Minnesota, shaken for a week by daily violence, officials believe that the unrest is created by extreme right groups, anarchists and local gangs.
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Mark Bray, a historian at Dartmouth University, is sure that anti-fascist activists participated in the violence, but it is impossible to know how small the cells are and act independently.
In the Washington Post the author of the book "Antifa: the Antifascist Manual" argues that "there are not enough anarchists and antifa activists to do so much damage".
Antifa on the terrorist list?
Justice Minister William Barr instructed the FBI to identify the organizers of the disorder, which he said was "domestic terrorism." But the anti-terrorist law only concerns foreign groups (IS, Al-Qaeda, Lebanese Hezbollah, Iranian Revolutionary Guards).
Even if pressure has increased in recent years to integrate American groups after attacks on the African-American or Jewish communities, some jurists worry about the risk for democracy if a leader is tempted to place political adversaries there.
Heard by Congress in February, FBI director Christopher Wray said investigations of far-right factions could be carried out by his anti-terrorist unit, as for IS supporters.
Extremist activists have been sentenced in recent years for threats or possession of explosives.
According to William Barr, the Antifa activists could be prosecuted by the American federal government for having crossed the borders between states, in order to participate in violence.
Justice could also be based on possible links of the Antifa movement with foreign organizations.