FORT COLLINS, Colo. - The Republican sheriff of Larimer County says he won't enforce federal laws that he considers unconstitutional.

Following recent mass shootings, President Barack Obama has proposed requiring background checks for all gun sales.

Larimer County Sheriff Justin Smith posted on Facebook that he wouldn't allow unconstitutional proposals to stand. Smith wrote that the only way to achieve universal background checks for private gun sales would be to register every firearm, which would mean people who fail to register could be defined as criminals. He contends the federal government will then start targeting and prosecuting Americans who are simply exercising their constitutional right to bear arms.