President Donald Trump signed an executive order Monday designating antifa as a domestic terrorist organization, formalizing his threatened attacks on political rivals and paving the way for a government crackdown on left-wing opponents.

The new order would require his administration to “investigate, disrupt and dismantle” individuals and groups associating themselves with the anti-fascist ideology antifa, including against “those who fund such operations.”

The order does not spell out what steps the government would take against the leaderless movement. Federal law enforcement has previously characterized antifa as an ideology, rather than a unified organization and the administration has not singled out specific individuals or groups it would target.

Labeling a U.S.-based entity as a terrorist organization also marks an unprecedented step since all of the 219 organizations with that State Department designation are foreign.

The announcement drew criticism from Rep. Bennie Thompson, the ranking member of the Homeland Security Committee. In a statement, the Mississippi Democrat called the order unprecedented and ignores the larger threat from right-wing extremism.

“Designating Antifa, which has no defined organizational structure or leadership, as a domestic terrorism organization is not only incorrect, it serves no purpose other than an excuse for the Trump administration to stifle dissent, investigate anyone, or any group, they don’t like, punish their enemies, and potentially label any American they want as a terrorist,” Thompson said.

White House press secretary Karoline Leavitt had previewed the order earlier, noting that Trump promised to designate antifa as a terrorist organization ahead of last year’s presidential election.

Trump’s rhetoric targeting political opponents has increased following the killing of Charlie Kirk in Utah earlier this month in what Utah law enforcement officials labeled a politically motivated attack.

Trump said in a social media post last week he intended to label antifa a domestic terrorist organization, calling it “a sick, dangerous, radical left disaster.”

Antifa, shorthand for anti-fascists, is an umbrella description for the far-left-leaning militant groups that resist neo-Nazis and white supremacists at demonstrations and other events.

Trump’s attacks on political opponents were a feature of his remarks Sunday at Kirk’s memorial service, where he blamed rising tensions in the wake of the activist’s death on the “radical left.”

“If speech is violence, then some are bound to conclude that violence is justified to stop speech. And we’re not going to let that be justified,” Trump told the audience in Arizona.

The order comes as Trump administration officials have sought to quash negative comments about Kirk following his death. Federal Communications Commission chair Brendan Carr pressured Disney into suspending “Jimmy Kimmel Live!” after the host made comments about Kirk on his show. Disney lifted the suspension on Monday.