These cops put their shooter in prison. Now they're going after the gun shop.

Two men walk into a gun store. One of them buys a Taurus PT140 pistol. A month later, the second one uses it to shoot two police officers in the face at point-blank range. Is the gun store to blame?

That’s the question at hand in an unusual trial that began this week in Milwaukee. The officers, who both survived and are still on the force, accuse Badger Guns of negligence for allowing 18-year-old Julius Burton to get his hands on a gun by paying someone else to buy it for him.

Experts in gun policy say it’s a shock the case even made it to a jury, given the gun lobby’s recent success in pushing laws that immunize manufacturers and dealers from liability in gun crimes in all but a few circumstances. But at a moment when gun control legislation is failing at nearly every turn, it gives a glimmer of hope for those seeking alternate methods of keeping guns out of the hands of criminals.

“This is an important lawsuit,” said Adam Winkler, a professor at UCLA and the author of Gunfight: The Battle Over the Right to Bear Arms in America. “Advocates need to put as much pressure on rogue dealers as they do on lawmakers promoting gun control.”

All she knew about the gun she bought was the caliber and that it was “pretty.”

It’s also a tough one to win, Winkler said. To do so, the officers must somehow prove that Badger Guns knew that the first man, Jacob Collins, was making the purchase on behalf of Burton, who was too young to do so and had an arrest record to boot. According to the lawsuit, Collins indicated exactly that on a transaction form before he was told by a store employee to correct the form and mark himself as the end user.

Attorneys for Badger Guns didn’t return requests for comment. In court this week, a lawyer for the store explained Collins’s correction on the form as a consequence of dyslexia.

But the plaintiffs say Collins was an obvious straw buyer: someone with a clean record who buys a gun for someone who can’t pass a background check.  A straw purchase is a federal felony, a statute narrowly upheld by the Supreme Court just last year in a decision written by Elena Kagan, who cited its dual purpose of keeping guns away from criminals and helping the feds catch bad actors. Without it, Kagan wrote, “Putting true numbskulls to one side, anyone purchasing a gun for criminal purposes would avoid leaving a paper trail by the simple expedient of hiring a straw.”

Straw purchases are the most common avenue of illegal gun trafficking, according to studies by the federal Bureau of Alcohol, Tobacco, Firearms and Explosives, which once found nearly half of all its investigations leading back to a straw buyer.

Gun retailers say spotting a straw purchase can be tough. Buyers often come accompanied by a friend or relative who may be more experienced with firearms. Sean Eaton, the owner of Fletcher Arms in Waukesha, Wisconsin, said his store has turned down sales on the basis of a suspected straw purchase a handful of times in the last year, and has been guided on spotting red flags by the National Shooting Sports Foundation, a trade association. “It’s an extremely difficult issue,” Eaton said.

In the Badger Guns case, lawyers said Burton pointed out to Collins the gun he wanted in a scene caught on surveillance footage. The store said its clerk didn’t notice.

Between 2007 and 2009, according to the suit, six Milwaukee police officers were hit with bullets from weapons sold at Badger Guns.

It’s not clear whether evidence like that will be enough to convict because there’s little recent precedent. In the last decade, the gun lobby has “slammed shut the doors of the courthouse” with legislation, said Adam Staggs, senior counsel for Everytown for Gun Safety, a nonprofit gun control group chaired by media mogul Mike Bloomberg. A centerpiece of that effort was the 2005 Protection of Lawful Commerce in Arms Act, which endowed gun stores with broad protections against liability lawsuits.

This is the rare case of a gun shop whose conduct is egregious enough to pose a serious legal challenge under that law, Staggs said.

Portions of Badger’s defense reveal how the operation on S. 43rd St. in West Milwaukee managed to stay in business despite regulatory heat. In a rejected request for summary judgment earlier this year, lawyers asked that “Badger Outdoors” be struck from the list of defendants. Badger Outdoors didn’t sell any guns to Collins, they said. That was Badger Guns. Under the Outdoors name, and the management of Walter Allan, Badger was the nation’s top seller of guns used in crimes in 2005, according to the ATF. The next year, under pressure from the ATF, Allan surrendered the license—and his son Adam hung up a new shingle, this one called Badger Guns, at the same location. Another shutdown in 2011 led to another license, this one for Mike Allan, Adam’s brother, who opened the shop under the name Brew City Shooter Supply and pledged tighter controls to keep criminals away.

Such arrangements are common. A Journal Sentinel investigation found 50 gun shops operated by family members of individuals who had had their licenses revoked.

Whatever its name, guns sold at Badger have persistently been linked to criminal activity. Between 2007 and 2009, according to the suit, six Milwaukee police officers were hit with bullets from weapons sold there. In 2008, a year before the officers in the current trial were shot, Sherrill Worthy was sentenced to three years’ probation for buying a gun there for her boyfriend, a convicted drug dealer. Worthy told officials all she knew about the gun she bought was the caliber and that it was “pretty,” according to the Journal Sentinel. Her boyfriend was later pulled over for speeding with the loaded .38-caliber revolver in his pocket, an ounce of weed, and his grandson in the front seat.

Witness testimony began on Thursday. If the officers prevail, it would be an exceptional victory, gun policy experts say.

In one extreme example of gun dealers’ built-in legal and legislative advantages, the parents of a victim of the 2012 Aurora, Colorado, movie theater rampage recently lost a case against the retailer of the guns used in that shooting. Not only did they lose, but a Colorado state law requires the victim’s parents to cover the legal costs incurred by the dealer: $220,000.

The Milwaukee officers’ shooter is serving an 80-year sentence for his crimes. Collins, the buyer, is serving a two-year sentence. But the officers presumably sense a greater injustice at play and a rare opportunity to slip through a crack in those courthouse doors.

Adam Auriemma edits the Justice section at Fusion.