ST. PAUL, Minn.- A Minnesota lawmaker wants to give cities to power to make some protesters liable for the cost of policing mass demonstrations.

Rep. Nick Zerwas, an Elk River Republican, said it's not an effort to discourage lawful protests. If his measure were to become law it would apply only to those convicted of unlawful assembly or disturbing the peace.

"There's a line between saying 'I'm advocating for this' to saying 'I'm shutting down this freeway.' Those are not the same thing," Rep.Zerwas told KARE.

State and local police agencies in St. Paul reported spending a total of $250,000 on officer overtime pay for staffing four Black Lives Matter protests last year.

Minneapolis Police Chief Janee Harteau said her department incurred $750,000 in overtime costs for the 4th Precinct protests last fall. Demonstrators set up an encampment at the police station on the city's north side for 18 days after a Minneapolis police officer killed Jamar Clark, an unarmed black man.

"There's a real cost to that for police. And currently that cost is being shifted to the local taxpayers," Zerwas said. "And local taxpayers shouldn't have to pay for that."

But "shut it down" has been the mantra of many of the demonstrations recently, and disrupting traffic flow is a strategy aimed at forcing average people to consider the message. The term "change the script" is often used by protesters to describe pushing beyond the limits of a parade permit.

Zerwas said he should be on solid legal ground because it's the same concept of the Dept. of Natural Resources seeking restitution from an arsonist for the costs of fighting a forest fire.

Not everyone agrees.

Chuck Samuelson of the ACLU of Minnesota said there's no free speech component to starting a forest fire.

"What this would is is chill free speech by various groups, particularly groups that aren't wealthy," Samuelson told KARE. "What he's trying to do is unconstitutional."

Samuelson said he worries such a law would be applied selectively, based on the messages of the groups involved.

"There's nobody to guarantee that they're not trying to bankrupt people who have unpopular opinions, and to shut them up that way."

There's also a perception among some that law enforcement agencies overreact to some protests, and bring in more resources than actually required.

"The government, the police department, gets to decide what's an appropriate response."

Zerwas said protesters who don't break the law have nothing to fear from his bill.

"If you disperse when the police tell you to disperse you're not affected by this," he explained.

"But if you say, 'I want to ruin someone's day!' that's different."