If the bill becomes law, prosecutors could charge people and seize assets for conspiracy to riot even if the so-called conspirators didn't participate in any violence.
As Phoenix New Times columnist Stephen Lemons wrote last week, the bill comes as a right-wing response to the violence and damage at recent protests in Washington, D.C., and on the campus of the University of California, Berkeley.
"You now have a situation where you have full-time, almost professional agent-provocateurs that attempt to create public disorder," Arizona State Senator John Kavanagh, R-Fountain Hills, told the Arizona Capitol Times.
News of the bill's passage in the State Senate shocked many Democrats and others who have found a much-needed outlet in public protests and demonstrations since the election of Donald Trump.
"Another attack on the right to protest," Jessica West, a Seattle law professor, weighed in on Twitter.
The bill, SB 1142, would add rioting to the list of offenses that could be charged under Arizona's Racketeer Influenced and Corrupt Organization laws.
As the State Senate fact sheet on the bill states, the RICO statutes allow prosecutors to take options like forfeitures when people are convicted.
The bill stipulates that an "overt act is not required as proof of a riot offense."
That means the planners of the protest could be charged because someone else committed an "overt act" that caused a riot. The bill also expands the definition of riot to include people causing damage to someone else's property.
Put that all together, and that means if a protest turns violent and damage occurs, the protest organizers could be held liable.
For example, if someone starts a fire that burns down a building, under the bill prosecutors could seek restitution by forfeiting the organizers' property.
Prosecutors could put liens on someone's home and seek recovery for the costs of the incident, which could "decimate" a person's financial holdings, said Rick Romley, former Maricopa County Attorney.
Another example that shows the absurdity of the bill, Romley said: Imagine a town hall meeting with a member of Congress, and one person gets mad.
"The person hits the wall with his hand, damages sheet rock — and [organizers] are potentially liable for bringing everybody there?" Romley said. "That's just wrong. It's insane."
The bill probably wouldn't be found constitutional by the courts, the Republican former prosecutor said.
Romley said that beyond that, the bill puts a chilling effect on the very idea of peaceable assemblies, which is protected under the U.S. Constitution.
State leaders "need to stand up and say 'this is wrong,'" he said.
Kavanagh, a former police officer, told the media that the law is needed to help prevent riots and damage by "anarchists" and others who plan for protests to turn violent.
After its successful passage by the State Senate on Wednesday, the bill was sent for review and possible vote by the State House of Representatives.
UPDATE: After pressure generated nationwide by this article and other media, the Arizona House later let SB 1142 die.