Just days after Governor John Hickenlooper signed Colorado's toughest gun-control laws in more than a decade, some sheriffs are denouncing them as unenforceable, even in a state that has seen two of the worst mass shootings in U.S. history.

The county-level officers say measures limiting ammunition magazines to 15 rounds and requiring background checks for firearm purchases are impossible to carry out because they're poorly written and don't clearly define the elements of a crime.

"I've taken a stance that I will refuse to enforce any law that violates peoples' constitutional rights," said Teller County Sheriff Mike Ensminger, west of Colorado Springs.

"We can't figure out how these laws would be enforced at this point in time without violating someone's constitutional rights," he said.

That stance reflects the view of hundreds of rural law-enforcement officials in states from California to Texas to Maryland who publicly proclaimed in the weeks following the massacre at Newtown, Connecticut's Sandy Hook Elementary School that they would defy new gun laws in the name of protecting their constituents' right to bear arms. That divide persists throughout the U.S. as the debate over tightened gun restrictions plays out in Congress and statehouses.