IMO the NRL will never let players get away with getting caught with/taking illegal drugs. It goes back to "mums not letting kids play a sport that is ok with players taking drugs".
Arguments about the drug debate doesn't matter, having 3 players and an executive in the headlines within 24hrs for taking coke is a publicity nightmare.
Perhaps say 4weeks for first offence, 8 weeks 2nd offence, 16weeks 3rd offence etc for getting caught taking/possession of illegal drugs and for significant alcohol-related offences (DUI, DV etc). In addition, 12month rep ban 1st offence, 2yrs 2nd, 4yrs 3rd etc.
During ban, a significant chunk of their contract (dependent on size) is held as a bond, returned after their ban is complete unless they re-offend during their ban.