Only a lawyer could even come up with this position.
Before the Fall, I don't know if God needed courts in heaven, but if He did, you know what Satan's profession was.
I know you are being facetious, but there is a strong element of truth in your joke. "Satan" means (roughly) "One who accuses" and in ancient Hebrew theology Satan was like a prosecuting attorney. If you look at the story of Job (without the interpretations and connotations that come from a Christian world-view) you can see that the Hebrews saw Satan as the angel tasked with bringing man's faults before God. Only later did that name become associated with the fallen angel/ultimate source of worldly evil in Judaic tradition.
So yes, Satan was (loosely) a lawyer and prosecutor by trade...