SEAN McNALLY did not want to leave the Portland Greyhound station that day in November 2011.

McNally had argued with a ticket agent, and security guards told him to leave. He refused; they called the police. Two responding officers told him to grab his bags and get out but, again, McNally refused, telling the police they couldn’t make him leave.

So the cops grabbed his luggage and placed it outside the station. An agitated McNally followed, lit a cigarette, and dropped it on the ground. When he bent over to pick it up, an officer put him in a headlock without warning. He submitted after a scuffle.

McNally never got on a bus that day. Instead, he was charged with second-degree trespass (for remaining in the bus station after being told to leave), resisting arrest (for the post-headlock scuffle), and interfering with a peace officer (for not listening to the cops). A Multnomah County jury convicted him on all three charges.

But that wouldn’t be the end of McNally.

Last week, the Oregon Supreme Court altered policing throughout the state when it agreed with the man that one of the charges against him was unlawful.

In a decision being lauded by civil rights advocates and defense attorneys, the state’s high court reined in how police officers can arrest people for interfering with a peace officer (also known as IPO), a Class A misdemeanor for people who don’t “obey a lawful order.”

The charge has long been used to ramp up legal consequences for individuals who otherwise commit minor crimes. In addition, IPO is used as a convenient tool for booking people into jail, since local authorities require a misdemeanor charge to hold someone at the Multnomah County Detention Center.

Protesting in the street after the police told you to leave? They could book you with IPO, as the Portland Police Bureau (PPB) did to at least 38 adults during the post-election protests in November and a handful of others since.

The charge has also been used to ramp up penalties against the homeless. As the Mercury reported in 2014, a short-lived pilot project by police and prosecutors involved targeting people for minor nuisance crimes (drinking or peeing in public, for instance) and using IPO to get them jail time.

That would be a lot harder today. The Supreme Court’s decision broadened an existing “passive resistance” exemption to the crime of IPO. Police can no longer arrest people for simply not cooperating with officers who give lawful orders, so long as those people aren’t violent and aren’t exhibiting “active conduct” after the order, such as running away.

Now, passively ignoring a cop’s orders simply doesn’t qualify for the charge. That goes for any circumstance, not just protests and demonstrations (though other relevant charges, like disorderly conduct or trespassing, can still apply).

This new reading of the law “criminalizes the obstruction of the work of the government and peace officers through active physical conduct, while at the same time broadly respecting constitutional principles of freedom of speech and assembly,” Chief Justice Thomas Balmer wrote in the April 20 opinion.

IPO is a “relatively common” charge, Multnomah County Deputy District Attorney Kirsten Snowden tells the Mercury. The official count for open IPO cases wasn’t provided by deadline, but Snowden says her office will review each case to determine which ones should now be dismissed, as is customary when the Supreme Court changes the interpretation of laws.

Asked how the new interpretation of IPO will impact the PPB’s protest policing efforts, bureau spokesperson Pete Simpson referred questions to the DA’s office.

“IPO has been frequently used as a cover-your-ass charge by the cops,” says local public defender Chris O’Connor, who touted last week’s ruling online.

“It’s important,” he says. “It’ll result in a lot fewer charges.”

Like O’Connor, ACLU of Oregon Legal Director Mat dos Santos says IPO has been one of the “catch-all” charges that police and prosecutors use to bust people when “there actually is no crime.” In addition to protesters, “there should be a significant impact to the houseless community, and also just people who are going about their lives in the over-policed communities of color in Portland.”

Defense attorney Matthew McHenry says IPO has been an easy charge for prosecutors to prove to a jury. He hopes last week’s court decision changes that—and as it happens, he might soon find out.

McHenry’s representing 66-year-old Margaret “Peggy” Zebroski, who’s facing IPO, resisting arrest, and disorderly conduct charges from a President’s Day street protest in February, during which she was slammed to the ground and bloodied by armored-up officers.

“I don’t think people should be criminalized for making their voices heard in ways that are nonviolent, and the McNally decision goes a long way towards that,” McHenry says.

He’s confident Zebroski will beat the disorderly conduct and resisting arrest charges, and thinks the ruling last week means she should also dodge an IPO conviction: “The McNally case seems pretty clear that if you’re ordered to get out of the street and you don’t, that’s considered passive resistance.”

Two other adults—Tristan Romine-Mann and Rebecca Smith-White—were also roughly arrested for charges that include IPO during the President’s Day protest. Prosecutors will soon determine whether they’ll continue prosecuting them for that.

“It gives me some hope that the Oregon judiciary is starting to strike the right balance between protecting people’s rights on the streets and protecting public safety,” dos Santos said. “In the past, the pendulum had swung in the opposite direction towards giving police absolute discretion, and these prosecutions would go forward without any thoughts.”