The Bulldogs became the first club to receive a breach notice for allegedly not complying with the governing body's new concussion guidelines during the round two match against Cronulla.

Half of the fine was suspended because the Jackson matter was a first breach. However, Fairfax Media can reveal the club has also received a ''please explain'' letter about the handling of James Graham's head knock in the round-four match against Melbourne.

It's one of three outstanding cases the NRL is looking at after clearing Penrith and Parramatta of breaches in the opening rounds.

Should the NRL determine there was a further breach by Canterbury, the Dogs could be up for $40,000 in fines and potentially face other sanctions, ranging from the loss of competition points to the deregistration of staff.

Canterbury officials are aggrieved about the initial fine and will appeal, claiming head physiotherapist Steve McCullagh was tending to a head cut suffered by Tolman when the Jackson incident occured.

NRL head of football Todd Greenberg explained the decision to reporters outside Rugby League Central on Wednesday. When asked if he believed the Bulldogs' physio was unable to attend to Jackson – and that the referees should have stopped the game – he said: "If you look closely at this incident, you'll see the referees did stop the game."

There was no suggestion of any wrongdoing by the Canterbury doctor, rather the NRL indicated the on-field staff erred by not referring Jackson to him.

“Player welfare is the absolute priority of everyone at the Canterbury-Bankstown Bulldogs and we are supportive of the NRL’s new rules surrounding the assessment of concussion,” Canterbury chief executive Raelene Castle said in a statement.

“We don’t agree with all the findings in the breach notice and, as per the process, will be using the next seven days to have those discussions with the NRL.”

The NRL said 27 players had been taken from the field in the first five rounds of the season to undergo sideline concussion assessments and 14 of them had returned to the field of play after being cleared.

The NRL will further consult with club chief executives, chief medical officers, coaches and players, as well as the Rugby League Players Association, in the coming months to hear their views on the way the policy is working.

"We made our policy pretty clear pre-season," Greenberg said. "Today is a line in the sand and shows we're fair dinkum about the policy and how we'll police the policy.

"By and large, I've been very impressed with the clubs, coaches, trainers, doctors with how they've applied the concussion policy this year. That's a good thing.

"As I've said a number of times, player safety is at the forefront of the decisions we make and that's evidenced by our decision today."

Greenberg congratulated the clubs for taking the concussion matter seriously and said he hoped players understood the new guidelines were introduced for their well being.

"The policy is designed to take players and place them in the care of the person most responsible, which is the club doctor," he said.

"That's the whole concept of the policy, it gives the opportunity, through the head trainer, to take players off and be assessed.

"Then it's up to the doctor; the person who is most qualified inside a stadium at a football match is the club doctor."

Greenberg said he had no qualms about taking action against his former club, where he was the chief executive before taking on the job at head office.

"I don't think it's got anything to do with a former club of mine," he said. "I'll make decisions irrelevant of the colours of the jerseys.

"That's what I've been charged to do and that's what I've done on this occasion ...

"We've made a clear decision today on a monetary fine, but there are wide-ranging sanctions available to us and we'll take them if appropriate."