It absolutely is, but violating an oath or duty isn't against the law. In a representative government, it is left to the people to excommunicate them, their peers to impeach them, etc. A fact that will surprise nobody is that the people in government spend a lot of time making laws that protect THEMSELVES, few have the character to pass laws they may ever be in danger of violating.

Add to this the complication/loophole that the Constitution is a living document, that changes and is re-interpreted regularly, and it's tough to get a rope on anyone for anything. They are taking full advantage of this now.