Dr. Casey Babb, terrorism professor and director of the Promised Land Project with Canada’s Macdonald-Laurier Institute, told Fox News Digital that policymakers already have the authority to curb homegrown extremism.

"Despite the First Amendment, and, of course, some of this is in a gray zone, but not all speech is protected," Babb said. "There are already tools there that enable policymakers, law enforcement, intelligence agencies and so on to crack down on domestic extremists." "Statements that are intended to provoke unlawful action, incitement, that’s not protected speech. Or statements where the person making [them] intensely communicate[s] some sort of intent to commit an unlawful act or violence, or says something that could be perceived as a legitimate threat, that’s not protected."

READ THE REPORT – APP USERS, CLICK HERE

The NYU report mirrors that frustration, concluding that the U.S. has "ample tools" to confront extremism but applies them unevenly. It found that when foreign terrorist designations restrict groups like al Qaeda and ISIS, their online reach collapses.

"The ability to designate organized nations and individuals as terrorist entities is a very useful tool," Babb said. "It’s a tool that policymakers should really lean into and think about, possibly modernizing and reforming to better address a lot of what we’re seeing domestically."

Babb said extremists are "learning from one another," adopting propaganda and recruitment methods once pioneered by Islamist organizations.

"Groups like ISIS, al Qaeda and the Muslim Brotherhood were some of the early adopters of these platforms," he said. "They recognized many, many years ago the power of these social-media outlets to recruit, to disseminate harmful messaging and to really undermine the populations that they target."

He also blamed social-media companies for enabling the spread of hate.

"There’s frankly no reason that I should be seeing much of what I’m seeing online," Babb said. "Free speech is one thing; giving a platform for nefarious state and non-state actors to spread divisive language deliberately with the intent of dividing Americans and endangering certain minorities, that’s something else entirely. These platforms reward outrage and they reward divisive content. A lot of people are monetizing this."

"You shouldn’t be making thousands of dollars a month by spreading the same messages that Adolf Hitler or Yahya Sinwar would spread," he added.

WATCH: Trump takes Antifa fight abroad with foreign terrorist designation

President Trump once floated designating Antifa a domestic terrorist group, an idea Babb believes deserves renewed attention.

"Designation opens a whole suite of tools," he said. "It makes adversaries’ lives much more difficult."

The Digital Aftershocks report concludes that U.S. policymakers and tech platforms must coordinate more aggressively to combat online extremism.