It's an oath to uphold a constitution that gives them no special right to usurp the laws of our democratically elected government. Elmer, if you take the SlickDeals Oath to Defend the U.S. Constitution™ with me, maybe we can decide which laws we want to follow too.
If the law of our democratically elected government are clearly immoral, in opposition to natural law, and in opposition to the constitution, they are illegitimate laws and the first priority is to restore the proper, constitutional government.
The constitution isn't that complicated or hard to interpret. Read some Locke, Jefferson, Mason, Madison, etc. and you pretty much have it. It only becomes hard and complicated when we want to find things that aren't there. That takes a lot of education and intelligence.