COLLINGWOOD'S blocking is perfectly legal according to the AFL's umpire manager Jeff Gieschen.

Fremantle coach Mark Harvey said on Wednesday he would seek clarification from the umpiring department, regarding the way Collingwood was blocking "a fair way off the ball".

Gieschen said he has since spoken to both Harvey and Collingwood coach Mick Malthouse and informed them there was no problem with the tactics the Pies have recently employed.

"If it was off the ball, we would have detected that in games," Gieschen told afl.com.au on Thursday. "All players at all clubs try to instigate blocks; sometimes a bit more than five metres off the ball.

"If the umpire sees it, they can be penalised for it being an illegal shepherd due to it being too far off the ball. From our perspective, Collingwood hasn't been breaking the laws there and if they had, they'd be penalised.

"It's quite clear what you can and can't do, and the whole aim of tightening up the interpretation of blocks and shepherding and the man on the mark is to make sure the player standing the mark, who is in a vulnerable situation, is safe."

Gieschen said the Magpies had been spoken to following their round two win over Melbourne after defender Harry O'Brien was seen to repeatedly engage with the man on the mark.

However, he said he was happy with the changes the Pies had made since that discussion.

"The key clarification points are that they can block when the ball is within five metres but in relation to the man on the mark, they can't block until the umpire calls play on," he said.

"Once that happens, Collingwood can send a player in to shepherd the man on the mark but I informed Mark that shepherd must be reasonable.

"I've spoken to Mick about it a couple of weeks ago and they're very well aware of what they can and can't do."

Gieschen said the Magpies' tactics would not be scrutinised any more than usual when they face Fremantle in a sell-out match at Subiaco on Friday night.

"We have observers at every game who watch for trends in what clubs do," he said.

"Our umpires are very well briefed on what can take place. Mark's raised it, Collingwood is aware he's raised it and we're aware he's raised it.

"He was just putting it out there in the public arena. We'd prefer the clubs seek clarification rather than go public but ... I don't see it as being a major issue."