A number of sheriffs around the country (Oregon, Kentucky, Missouri, Wyoming, New Mexico, Utah) have said they will refuse to enforce federal restrictions on private gun ownership that they find to be in conflict with the Constitution.
It seems like a bold threat, but it really isn't. State and local law enforcement officials simply don't have to enforce federal laws that they don't want to enforce. That fact is not controversial. It is, however, a persistent issue in the federal versus state struggle over the marijuana legalization initiatives in Colorado and Washington. Those states have simply chosen to stop assisting the federal government. It may complicate the feds' ability to enforce those laws, but it's just not as confrontational an approach as media reports have suggested.
Robert Mikos discussed this in his new paper with respect to marijuana laws, but the principles related to how states and federal powers interact is one that holds significant implications for the right to keep arms and the President's health care law.
Mikos and I discussed the marijuana initiatives for a Cato Daily Podcast. You can also watch the forum.
Tim Lynch and I also discussed gun restrictions and federalism in a Cato E-Briefing last week.