Ohio pro-gun groups filed a lawsuit Thursday against Columbus and Cincinnati, hoping to overturn recently passed gun control measures.

In May, Cincinnati City Council became the first Ohio city to ban bump stocks. Columbus City Council followed by unanimously approving a slate of 11 gun ordinances.

Among the ordinances are a ban on accessories like bump stocks, restrictions on the sale of imitation firearms, and a prohibition of gun sales in residential areas.

The Buckeye Firearms Association and Ohioans For Concealed Carry, which filed companion suits against both cities, argue it's illegal for them to pass any such restrictions. A 2006 state law blocks municipalities from passing gun control measures more restrictive than Ohio's regulations.

"These lawsuits are not about the bump stock per se, it's about the rule of law in Ohio," says Dean Rieke, executive director of Buckeye Firearms. "Because it's our belief that they're passing these laws as a test to see what they can get away with."

Bump stocks are attachments that make semiautomatic weapons fire like automatic weapons, and were used during last October's mass shooting in Las Vegas. Columbus also prohibited the possession of weapons by people convicted of misdemeanor domestic assault or are the subject of protection orders.

City Attorney Zach Klein plans to defend Columbus’ laws, arguing they simply fill in the gap between state and federal gun regulations.

“We believe that we are operating within the plain language exceptions of the Ohio Revised Code in making sure that domestic violence abusers who have been convicted in the court of law cannot possess weapons in the city of Columbus,” Klein says. “For a lot of reasons, federal law is not enforced by the Department of Justice, so Columbus is stepping up to enforce its own law that mirrors federal law.”

Rieck dismisses that defense.

"They think that they found a loophole. And we believe that they're wrong," Rieck says. "Basically, they're playing a word game."