The NRL's decision to revert to a one-referee system threatens to turn ugly with the referees' union taking the dispute to the Fair Work Commission.
Professional Rugby League Match Officials on Thursday claimed the league had no right to change the officiating model under the current enterprise agreement.
They have engaged the services of Harmers Workplace Lawyers.
PRLMO chair Silvio Del Vecchio told AAP they are confident of getting the NRL to overturn Wednesday's decision and go back to using two on-field referees before the May 28 season restart.
"We have filed to Fair Work for conciliation and potentially arbitration in order to restore what we think is the right structure," Del Vecchio told AAP.
"More importantly, it's to uphold an enterprise bargaining agreement that we, in good faith, had in place between the PRLMO and the NRL.
"The NRL have not adhered to this agreement."
The PRLMO says that, under the terms of the four-year agreement, which began in 2019, the governing body must persist with the two-referee system.
In a letter sent to the ARL Commission on Wednesday, the union presented a number of reasons why any rule change required more consultation.
They included duty of care to players and match officials, best interests of fans and sponsors, and potential errors in calculation of financial savings.
Cost saving has been a key given by ARLC chair Peter V'landys to move back to one referee, while he also says it has the backing of fans.
All refs remain employed: V’landys
V'landys has guaranteed all 22 full-time referees will remain employed.
However Del Vecchio calculated that, even if the NRL terminated all eight of its casual whistleblowers, the savings amounts to less than $300,000 a year.
"We've done the maths. When you average it out over the course of the remaining games of the year, it equates to $20 per minute of each game," he said.
"It's just peanuts. It's unnecessary.
"More importantly, they haven't consulted with us. We can recommend different ways to save a lot of money in the NRL in the refereeing department.
"But they haven't been working with us."
The referees union also argue that the league has often preached about the "superiority" of the two-referee model, as recently as last year's grand final.
Del Vecchio went on to claim that more than 80 per cent of play-the-ball infringements and illegal tackles are made by the pocket (second) referee.
Asked whether the referees would take strike action if a resolution can't be reached before May 28, he said: "We'll assess it at that time.
"I guess we will need to take the right advice. We are confident that we will be in a position to proceed by the 28th of May."