The Constitution does not give anybody any "rights." If you read it carefully, you will see it says "the right of the people to keep and bear arms shall not be infringed." The "right" pre-existed the Constitution. People, like all living creatures, have the right to defend themselves. The Second Amendment confirms the people's right to collectively defend ourselves from tyranny, which a war had just been fought to relieve, It does not mention hunting or sport shooting. Mr. Thompson asks the question, who needs a 30-round magazine, and the answer is obvious, someone facing an enemy with a 30-round magazine.
Recent natural disasters have shown the ineffectiveness of the government to defend people's property when domestic infrastructure has broken down. All our major cities are as vulnerable as New Orleans if such an event should occur there. To limit the ability of these or any living soul to defend themselves will lead to innocent fatalities. An armed society is a polite society.
This statement leads to the next point, mass shootings almost always occur where firearms have been banned. Mr. Chambers points out the shooter in Arizona had emptied his 30-round magazine. Had a defensive firearm been present, he may not have had opportunity to do so.
For the sake of brevity and arbitrary letter policy, I will omit other pertinent discussion, and skip to the "pledge" issue. The office of sheriff is very old, going back to common law England. He is the original elected law enforcement officer in his county and has authority over law enforcement. Sheriffs were enforcing law before there was a Constitution. He not only has the authority to defend the people's right to keep and bear arms, he has the obligation. Not being beholding to the federal bureaucracy, he is, in fact, free to independently interpret the acts of Congress. He took an oath in common law jurisdiction to defend and protect the Constitution from all enemies, including those in D.C. The Constitution clearly states "the right of the people to keep and bear arms shall not be infringed."
The Constitution is the rulebook for the federal government. Congress has no authority to pass gun-control legislation, being expressly forbidden by Constitution. The sheriff's oath requires him, correctly, to uphold the higher mandate.