Boulder’s new ban on assault weapons is already being challenged in court.

The ban – city Ordinance 8245 – was passed unanimously by the Boulder City Council. It bans sale and possession of guns the city defines as assault weapons along with bump stocks (a.k.a. “multi-burst trigger activators”) devices that allow a gun to be fired rapidly) and large magazines.

The lawsuit, filed Thursday in federal court, claims the ordinance “violate[s] multiple provisions of the U.S. Constitution including Article VI, the First Amendment, the Second Amendment, the Fifth Amendment and the Fourteenth Amendment.”

It was filed by Jon Caldara of Boulder – a broadcast host and president of the Independence Institute, a libertarian think tank – as well as the Boulder Rifle Club.

Attorneys from the conservative Mountain States Legal Foundation are representing the plaintiffs.

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Under the ordinance, Boulder defines “assault weapons” as:

All semiautomatic rifles that have the capacity to accept a detachable magazine and that have any of the following characteristics: a pistol grip or thumbhole stock; a folding or telescoping stock; or any protruding grip or other device to allow the weapon to be stabilized with the non-trigger hand.

All semiautomatic center-fire pistols that have any of the following characteristics: the capacity to accept a magazine other than in the pistol grip or any device to allow the weapon to be stabilized with the non-trigger hand.

Any firearm that has been modified to be operable as an assault weapon as defined by the city, plus any part or combination or parts designed to convert a firearm into an assault weapon.

Under the measure, Boulderites would have 30 days to get rid of bump stocks and until the end of the year to dispose of high-capacity magazines. The ordinance would exempt law enforcement, military personnel and federal officers.