The laws "severely restrict citizens' rights to own, use, manufacture, sell, or transfer firearms and firearms accessories," the sheriffs said in their complaint in the U.S. district court.

"This is a bipartisan effort," said Larimer County Sheriff Justin Smith. "These are Democratic sheriffs and Republican sheriffs who came together."

The National Shooting Sports Foundation, magazine-maker Magpul Industries, and the Colorado State Shooting Association were among other groups that filed suit alongside sheriffs against the laws, which are set to take effect June 1.

Scarred by some of the deadliest incidents of gun violence in American history, including last year's Aurora movie theater shooting and the 1999 shooting at Columbine High School, the state's gun control bills gained national attention as various states and the federal government debated new gun restrictions.

The sheriffs said in the filing that their ability to enforce the laws, particularly the ban on magazines that hold more than 15 rounds, will be constrained by other concerns.

"The Sheriffs have limited resources and limited public funds to spend on investigations," they said in the court documents. "They cannot expend those resources to conduct investigations that would be necessary to monitor compliance with the new magazine restrictions. No documentation has ever been required for the retail or private purchase of magazines, making it a practical impossibility for the Sheriffs to determine whether one of the many magazines already in existence was obtained after the effective date."

The sheriffs also said that Coloradans would find it difficult to comply with expanded background check regulations that would require transfers between individuals to be conducted through a federally licensed firearms dealer. That's because many licensed firearms dealers in the state "are unwilling to conduct the transfer under such conditions," they argued.

Colorado Attorney General John Suthers released a statement on Friday saying that his office would pursue court rulings on the gun legislation “as expeditiously as possible.”

“Colorado citizens, and law-abiding gun owners in particular, deserve such clarification,” Suthers said in the statement.

The state has 64 sheriffs, said Chris Olson, executive director of the County Sheriffs of Colorado. The lawsuit is being brought forth “by individual sheriffs” and his organization is not a party to the suit, he said.

At least one lawman has said that deciding which laws are constitutional should stay out of the hands of Colorado’s sheriffs.

Arapahoe County Sheriff Grayson Robinson, whose county includes the Aurora movie theater where 12 people were killed last year, released a statement in January pushing back against sheriffs who said they would not enforce new gun laws.

“Public safety professionals serving in the executive branch do not have the constitutional authority, responsibility, and in most case, the credentials to determine the constitutionality of any issue,” Robinson said in the statement. “Law enforcement officials should leave it to the courts to decide whether a law is constitutional or not.”

Robinson identified himself as a supporter of Second Amendment rights in the statement, and said he would like to see better mental health services and stricter penalties for people who commit gun crime