You seem to have things bass-ackeward. Davis served in the U.S. Senate. He was not a servant of the federal government. He was a servent of the people of Mississippi.
If a case could have been made against Davis, it would have been attempted. It was not. Perhaps all they needed was your legal expertise to carry it out. Legal experts of the day, lacking your expertise, knew it was a loser and that pursuit would rend the nation asunder.
Stop trying to redefine words to mean what you want them to mean, the way the Southern Cabel wants to redefine reality.
Take a look, joker - it is you attempting to alter the definition of treason.
Leading it in rebellion against the U.S is treason.