Definitions for ease of reading: POTUS = President of the United States
SCOTUS= Supreme Court of the United States
My answer in length posted now - people need to be MAD, get ANGRY feel SOMETHING!!! I don't claim to understand all the issues and reserve the right to be wrong. Notwithstanding I totally disagree with the surmise of the author, who is basically saying; Sheriffs do not have the right to choose which laws to uphold.
LAW enforcers are required by oath to uphold our (YOUR) constitutional rights. The Supreme Court has already ruled on the right to bear arms and assault weapons previously and confirmed the constitutional right to bear arms - including assault weapons. So the Sheriffs (even if I am not thrilled with much of the actions) are correct to NOT act in opposition to the rights granted in the constitution (not to mention upheld by SCOTUS).
While in 2008 there was some ambiguity left in the SCOTUS ruling as to the ability of States and Feds to limit types of weapons; there was not assault weapon ban passed by SCOTUS, as pointed out by Mcclatchy DC.