I understand that it failed before but the only major stumbling block would be getting the RLPA on board which wont be an issue once you show them the potential money they could be pocketing.
The problem with a draft is pretty much the same as it was back in 1991, when 154 players took the NSWRL to the Federal Court. The main things that have changed are that back then it was NSWRL trying to introduce a draft and the Salary Cap wasn't the same for each club. The NSWRL decided the Cap based on their assessment of how much each club could afford to pay its players, the lowest Cap was $800k and the highest $1.5m (pretty scary, huh?). This was their main reason for introducing the draft, so that the clubs with the higher Cap wouldn't keep getting the best players. This reason is now gone, the Cap is the same for everyone, according to the NRL rules anyway. Hence they can hardly go to court and argue otherwise.
The RLPA argument is however still exactly the same, a draft removes choice from a player (an employee) and forces them to play for a club (an employer) that they might not have otherwise chosen. Additionally it would inevitably lead to young players being forced to move thousands of kilometres away from their families and support networks. There is a personal social cost in doing that.
Think about it in the context of your own situation, you (or your children or your grand children) have just finished the HSC and some guy that you may have never met walks up to you and says "Hi, I'm your new Coach, we won the raffle (which is what a draft is, just rigged a bit) and you are moving to Townsville next Monday when pre season training starts". Then on Sunday night, "Sorry, we traded you and you are going to Auckland tomorrow".
We all get to choose our employer, it's part of living in a democracy, I don't see any Court changing that any time soon.
Go Dogs