Colorado sheriffs upset with gun restrictions adopted in the aftermath of last year's mass shootings filed a federal lawsuit Friday, challenging the regulations as unconstitutional.

The lawsuit involves sheriffs from 54 of Colorado's 64 counties, most representing rural, gun-friendly areas of the state.

The sheriffs say the new state laws violate Second Amendment protections that guarantee the right to keep and bear arms. Opponents are criticizing the lawsuit as political maneuvering.

The filing targets Colorado laws that limit the size of ammunition magazines and expand background checks. The regulations passed the Legislature this spring and are set to take effect July 1.

It isn't yet clear whether the sheriffs' challenge will delay or jeopardize the laws. The filing, however, guarantees the renewal of a fierce debate over gun control.

Colorado lawmakers passed the restrictions in reaction to the shooting rampage at a suburban Denver movie theater last summer, where 12 people were killed and dozens more were wounded, and the massacre at an elementary school in Newtown, Conn.

The gun control debate was one of the most emotionally charged of the legislative session, with lengthy debates and national attention. President Barack Obama added to the attention on the Colorado Statehouse, as his administration unsuccessfully pushed Congress to enact similar gun controls.

Sheriffs' attorneys are considering whether to ask the court for a preliminary injunction, which would block the Colorado laws while the lawsuit moves forward.

The law enforcement community is divided on the issue. In contrast to the sheriffs, the Colorado Association of Chiefs of Police, which includes urban departments, supports the laws. The chiefs said the measures were "common-sense approaches" to protect the public "while not taking guns from law-abiding citizens in any way."

Unlike sheriffs, police chiefs are not elected.

Democrats maintain the public is on their side, and say legislators carefully crafted the proposals that were signed.

"These laws were not constructed haphazardly," said Democratic Sen. Mary Hodge, the sponsor of the magazine limit. "They were constructed to protect us from massacres like the ones we suffered in Aurora and Newtown."

Relatives of victims of the Colorado shooting criticized the sheriffs for filing the lawsuit and accused them of playing politics.

"As a parent who lost my son Alex at the Aurora theater shooting, I ask these people to put themselves in my place," Tom Sullivan said in a statement. "I do not understand why these politicians are picking guns over people."

Weld County Sheriff John Cooke said he and his colleagues were "not the ones playing politics with this."

"We believe that the Legislature were the ones who were playing politics," he said.

Gun control opponents say the language in the regulations is unclear and doesn't provide safeguards to prevent people from inadvertently breaking the laws.

Ammunition magazines, for example, are easily converted to larger sizes, which the bill bans. Gun rights advocates also say the law expanding background checks doesn't provide enough exemptions for temporary transfers and that people conducting private transactions will have a difficult time getting appropriate checks.

Lawmakers allowed several exemptions in the background check legislation, including transfers between immediate family members, shooting events and temporary transfers of up to 72 hours.

State officials, including Attorney General John Suthers, have worked to defend the intent of the laws. Suthers, a Republican responsible for defending the law against the legal challenge, issued a statement Friday giving guidance to law enforcement on how the magazine limit should be enforced.

He said magazine features "must be judged objectively" and that magazines that hold 15 rounds or fewer can't be defined as "large capacity" simply because it can be modified to include more.

The state has 30 days to respond to the lawsuit.