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...
But was I being facetious? I don't know. I seriously think that a lot of lawyers worship Satan, in their hearts, not necessarily in cultic activity.
But then that can be said of all sorts of people. Lawyers just seem to be able to do more damage to society than most other professions.