Yes, but it would be up to an individual player to sue the NRL and prove that the NRL’s decision was wrong — effectively forcing a player to set the precedent. The NRL can set its policy knowing it’s highly unlikely to be challenged.No case law to support that theory so would need a bright Lawyer to set precedent.
With the rule made clear in advance, the high cost of setting a legal precedent, and the reputational damage a player would face - being portrayed as someone who chased the R360 money and is now trying to return - it’s unlikely any player would challenge the policy.
Even if a player did take the NRL to court and had a strong case, the NRL could simply argue that the player is no longer of NRL standard due to time out of the game and the different skill set. That would reduce potential damages, creating an even greater barrier to legal action.