The Sydney Roosters have been issued two breach notices, each proposing a fine of $20,000, for incidents involving criticism of the referees at Monday's Anzac Day match against the Dragons.
In the first incident, Roosters coach Trent Robinson allegedly approached and harassed referee Ben Cummins in the Allianz Stadium tunnel at the end of the match.
In the second incident, Mr Robinson attacked the credibility of Mr Cummins in his post-match press conference.
NRL CEO Todd Greenberg said both incidents were potential breaches of the NRL rules and the club would have 7 days to respond to the breach notices before a final determination was made.
"We cannot stand by and allow any club to deliberately and blatantly attack our referees," Mr Greenberg said.
"Not only is it a breach of the rules which are there to protect our referees from abuse, but it sets a bad example to the rest of the game, particularly juniors.
"We know from experience that young people imitate their NRL heroes and attacking referees is simply not acceptable.
"We are also trying to encourage young people to become referees and public attacks like this do nothing to achieve that goal."
Mr Greenberg said the NRL recognised that referees, like players, make mistakes in games and it was not surprising that clubs were sometimes frustrated by calls which went against them.
"But there are proper channels to vent those concerns and they were not followed in this instance," he said.
"Our referees boss, Tony Archer is happy to talk to any club about issues which arise out of a game and that is the right way to address any problems."