posted May 17, 2013 10:49 PM            

The two laws, passed by the state's Democratic-controlled legislature with scant Republican support, ban ammunition magazines that hold more than 15 rounds and require background checks for all private gun sales and transfers.

All but 10 of the state's 64 county sheriffs signed onto the suit, filed in U.S. District Court in Denver. In their complaint, the sheriffs allege the new laws, which go into effect July 1, "severely restrict" citizens' constitutional right to own and bear arms.

The sheriffs, who in Colorado are elected, also complained that they were operating under tight budgets and did not have the money or manpower to enforce the new laws.

"They (the sheriffs) cannot expend these resources to conduct investigations that would be necessary to monitor compliance," the lawsuit said.

The bills were introduced in response to a shooting spree that killed 12 people at a suburban Denver movie theater last July and the slaying of 20 children and six adults at an elementary School in Newtown, Connecticut, in December.

Connecticut and New York have also passed stricter gun laws in the wake of the shootings. The National Rifle Association, the powerful U.S. gun lobby, has announced plans to challenge the new gun control laws in all three states.

Democrat state Senator Mary Hodge, who sponsored the magazine-limit bill, blasted the sheriffs and said the restrictions were reasonable public-safety measures.

"We can't just sit by and do nothing while first-graders and moviegoers are being mowed down in one fell swoop with weapons equipped with large-capacity magazines," Hodge said in a statement.

Joining the sheriffs in the lawsuit are a number of gun-rights organizations and a disabled gun owners group, who say that magazine limits would restrict their ability to defend themselves in violation of the Americans with Disabilities Act, which bars discrimination against the disabled.

"Disabilities make it difficult to quickly change magazines under the stress of a home invasion," the lawsuit said.

Governor John Hickenlooper, a Democrat who signed the bills into law, is named as the defendant in the lawsuit. His office had no immediate comment.

Colorado Attorney General John Suthers, a Republican, said in a statement that his role "will be to get court rulings on the legality of various aspects of the legislation as expeditiously as possible."