My take on this and other court decisions is that, County Sheriffs have no power or obligation to enforce a federal statute. Federal laws are to be enforced by federal agents/prosecutors.
There are many federal laws which have state/local mirrors, these are the laws that county sheriffs are charged with enforcing.
NRA Lifetime Member Since 1999
"I ask, sir, what is the militia? It is the whole people except for a few public officials." George Mason