The NRL would have final approval of what gets used, not so much telling them what they have to wear. They would be more stringent on getting heritage jerseys as accurate as possible on a modern uniform. That would mean no butcher stripes with piping and a teardrop for the dogs, no incorrect shorts and socks for the Knights and no completely made up history for the Warriors.
Teams like the Roosters, Knights and Panthers dropping unpopular jerseys before the 2/3 years are up means that fans who bought those particular jerseys now have an out of date design and would need to shell out another $160 in order to be up to date. Granted that this isn't everybody's priority but I'm sure kids in particular would like to be able to wear what their heroes wear. Although it sucks for the Knights, they would be made an example of and would serve as a warning to other clubs. They're on their 3rd year of that jersey (I think) so this would be its year if they choose. Not so bad considering in leagues like the NFL, teams keep uniforms for a minimum of 5 years. And come 2013, the Knights will either pick a damn good jersey, or screw it up for the next 3 years.
On another note, whoever is in charge of the Tiger's gear needs to be shot...