As Donald Trump threatens legal action against his adversaries, particularly after Charlie Kirk’s assassination, he’s repeatedly talked about using one federal law: the Racketeer Influenced and Corrupt Organizations Act, or RICO.

Trump wants to bring racketeering charges against left-wing groups he’s accused of promoting violence. Some influential Republicans agree with him and have been pushing to include rioting as one of the crimes that falls under the racketeering statute, a decades-old law once aimed at cracking down on organized crime.

Kirk’s death and the resulting calls by influential conservatives to crack down on the left using the federal government’s official powers has called new attention to that push. Trump and his aides have said publicly they plan to channel the mounting conservative anger over Kirk’s killing into efforts to take on the president’s political rivals, including potentially pursuing RICO charges and seeking to designate some liberal groups as domestic terrorist organizations.