The NRL says coaches, players and club officials will be banned from making any public comments on the performance of referees this season.
In previous seasons, the league's code of conduct banned "excessive criticism" or "attacking the integrity of the referees".
"In simple terms, we have taken out that grey area. The rules are now plain and clear," NRL head of football Todd Greenberg said in a statement only hours before Thursday night's season opener between Brisbane and South Sydney.
Clubs and individuals risk a breach notice if they fail to follow the revised rules.
The NRL says the move is designed to support the men in the middle and encourage more people to become referees.
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The change was discussed in December with all 16 NRL head coaches and at the recent CEOs meeting in Auckland.
Greenberg said referees would still be held accountable.
"We're not looking to protect our match officials, we are looking to provide leadership for them," Greenberg said.
"Being critiqued by coaches publicly is not the way the game should be played and it attacks the integrity of the game.
"Coaches and clubs have used referees to their advantage to deflect attention or steer the debate a certain way.
"Our referees will still be held accountable for their performance. Our internal review processes are extremely thorough, and clubs and coaches will have regular communication with our referees elite performance manager Tony Archer."
