"This ban is tantamount to Boulder attempting to stop drunk driving by banning Subarus", said foundation attorney Cody J. Wisniewski. The group says a recent ordinance passed by the council violates the USA and Colorado state constitutions. "It accomplishes nothing other than making criminals of law-abiding citizens".
The ordinance bans "assault weapons", which the council defined as semi-automatic rifles with pistol grips or thumbhole stocks, or a folding stock, or a stabilizing grip for the non-trigger hand.
A legal group plans to challenge the ban on the sale or possession of assault weapons in Boulder.
They filed the lawsuit in federal district court in Denver, Colorado.
Council members have claimed a home-rule exception in defending the ordinance, which includes exemptions for military, law enforcement and competitive shooters.
Current owners will be grandfathered in to keep the guns they already have, according to the network.
"The point here is that this Supreme Court opinion from 2008 makes it very clear that we can regulate weapons designed primarily for human destruction", said Council Members Sam Weaver and Bob Yates in an opinion piece for the Boulder Daily Camera. "And because it's the right thing to do".
"It relates to an issue over which municipalities have virtually no control", said the April 4 editorial.
While Colorado has trended blue in the last couple of decades, the state also hosts a booming hunting industry and widespread gun ownership.