Trump has already said he planned to designate Antifa as domestic terrorists. Some are opposed to such a move, like this article from RAND.

One problem with that report; its author says at present the US only has a Foreign Terrorist Organisation list and "Antifa does not clearly meet the definition of the F, the T, or the O."

Since when?

Foreign: They are not American, it's an international movement following the same principles, waving the same flag and wearing the same identifying marks.

Terrorist: They've been using violence to silence political opposition for years. It is their entire raison d'etre. And if the past week hasn't show someone that they've escalated to killing people, that person's motivations are suspect.

Organization: These people don't suddenly appear in crowds through sheer happenstance. They coordinate activities online and have the same loose cell-based structure that all terrorist groups do.

The RAND article is a joke; hopefully someone in the Executive and/or Homeland will have more grit.