Police may be given power to arrest anyone involved in a peaceful demonstration that is merely suspected of turning violent.
Republican senators in Arizona voted for SB1142 this week, which proposes expanding the state’s racketeering laws to also include rioting.
It will permit police to arrest people who are at least involved in planning a protest.
“Wouldn’t you rather stop a riot before it starts?” asked former police officer and Senator John Kavanagh during the debate, according to the Capitol Times.
“Do you really want to wait until people are injuring each other, throwing Molotov cocktails, picking up barricades and smashing them through businesses in downtown Phoenix?
“You now have a situation where you have full-time, almost professional agent-provocateurs that attempt to create public disorder.
“A lot of them are ideologues, some of them are anarchists. But this stuff is all planned.”
Fellow Republican Senator Sylvia Allen added: “I have been heartsick with what’s been going on in our country, what young people are being encouraged to do.”
Americans have recently protested after a Los Angeles police officer fired his gun while surrounded by teenagers.
Police also made arrests when 75 demonstrators refused to leave a Dakota Access pipeline protest camp.
Many of the 230 protesters arrested during Donald Trump’s inauguration last month, some who faced charges of felony rioting, claimed they had done nothing wrong.
Democrats in Arizona accused their rival politicians of trying to stifle First Amendment rights, and pointed out there were already laws criminalising actual rioting.
Senator Steve Farley said: “[It] will have a chilling effect on anybody, right or left, who wants to protest something the government has done.”
Republicans voted by 17 to the Democrats' 13 in favour of the bill on Wednesday.
It will now go to the House of Representatives for approval.
The Independent has contacted Arizona GOP chairman Jonathan Lines for further comment.