Ok, that's 7 votes for the combined penalty proposed by majicmg.
1st offense - Simply drop the offending player IMMEDIATELY upon discovery, replace him on the roster and use a benchwarmer valued at under $1 million in his place for the same number of games the ringer played.
2nd offense - Follow the same procedure as in offense No. 1, while adding an additional financial penalty equal to the offending player's salary. The owner will regain the cash when the games-played penalty expires.
3rd offense - Follow the same procedure as in offense No. 2, but double the financial penalty.