Kangaroos midfielder Jy Simpkin was handed an official warning by the AFL after he called the league and MRO "laughable" for the three-match ban handed to Paul Curtis.
Gold Coast coach Damien Hardwick was also put on notice after venting his displeasure about umpiring decisions following his side's loss to Geelong two weeks ago.
It's believed the league have now told clubs that fines will be handed out for the next instance of criticism of umpires, match review decisions or the tribunal.
North coach Alastair Clarkson says his players are well aware of the consequences.
"We gave our players another reminder yesterday that the rules and regulations were in place for a reason, and whether we like them or not, they're the rules we signed up for at the start," Clarkson said.
"(If) we want to be contracted into this game, the game that we love, then abide by the rules and regulations that are there."
Clarkson himself has copped a series of fines over his decorated coaching career for incidents ranging from conduct unbecoming to criticism of umpires.
"We enter society and there's rules and regulations, and sometimes we choose to flaunt them and you pay the penalty if you break them," Clarkson said.
"That's the same with AFL footy. We know the rules and regulations are there, and sometimes we'll choose to ... violate them and be prepared to cop the fine for being prepared to say something you think is really important.
"I've been at the back end of that a couple of times, and have chosen to speak my mind and it's cost me a bit out of my wallet.
"So I've been given a gentle reminder by my wife more than once that I'm better off just doing it behind closed doors."
Meanwhile, Clarkson is optimistic talks will keep progressing with Charlie Comben as the incoming Tasmania club circle the star defender.
Comben is contracted with the Kangaroos until the end of 2027 and they are desperate to keep him.
"Even though the actual signature hasn't been done yet, the discussions have already commenced," Clarkson said.
"He would have been thinking about it, we've been thinking about it. So we'll at some point in time get together and hopefully work that out pretty soon."
North Melbourne (7-7) will be aiming to make it three wins on the trot when they face Essendon (1-13) at Marvel Stadium on Sunday.
The Roos will be without ruckman Tristan Xerri after he suffered a fractured jaw during last week's 25-point win over Richmond.
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