Wallabies captain George Gregan has called for a rugby league-style judiciary system to be introduced for international rugby, claiming infringement penalties were a mystery to players.

The two-week suspension for Scotland lock Stuart Grimes for trampling has divided many but Gregan suggested the major thing to come out of it was that rugby needed a coherent judicial system.

"That's probably the inconsistency of rugby union. We don't have any guidelines, say a shoulder charge is worth X amount of weeks and what grade it is," said Gregan ahead of Saturday's second Test against the Scots at Telstra Stadium.

"I think we are a little bit behind other sports in terms of that."

Gregan said the National Rugby League system of grading offences according to their severity had merit, describing it as at least setting "a framework which you can work under."

"Ours is very loose, you can get a guy getting two weeks for that and then a week later someone will come up and get five weeks.

"For what you think is a similar offence it can be quite a big discrepancy in the length of time away from the game."

Grimes had been cited after referee Paul Honiss let the incident go on the field, the lock rucking vigorously on a prone Australian No.8 David Lyons who was clearly impeding the path of the ball.

Scotland coach Matt Williams said the backlash would come on the field with his side fired up over the incident.

"We are all gutted," Williams said.

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