has found himself smack-dab in the middle of a real-life "Sons of Anarchy" storyline ... as the feds try to nail a biker gang on racketeering and conspiracy charges.
The legendary pro wrestler and former Minnesota Governor appeared in an Orange County courtroom Wednesday to testify on behalf of the Southern California-based Mongols Motorcycle Club ... of which he's an inactive member.
He was called as an expert witness for gang members who accused of murder, drug running, robbery, extortion and other crimes. Jesse said under oath when he was a member of the MC he never engaged in criminal activity.