I know the Toydarians don't have anything mechanics wise that says they are immune, but it is in the fluff and I believe the devs said this was intentional to let GMs decide how to do it.
Also, what force powers would you allow use of on a droid? Obviously not sense or influence, but bind? Could you bind a droid? If you bound a droid, could you disorient it with the strength upgrade?
How have you guys run this (or encountered it as a player) before?