THE AFL says the correct decision was made not to award Richmond star Dustin Martin a 50m penalty in the dying stages of the Tigers' three-point loss to GWS on Saturday.

With just under three minutes remaining in the game, Martin took a mark just outside the Tigers' forward 50m arc.

Greater Western Sydney forward Jeremy Cameron stepped in to man the mark, and as Martin took the kick, his teammate Shaun Grigg attempted to shepherd the Giant away. 

Cameron then moved forward on an angle to step around Grigg, smothering Martin's kick.

With no 'play on' call, some commentators were baffled by the umpire's decision not to pay a 50m penalty to Martin, as they considered Cameron had stepped over the mark.

But a spokesperson for the League's umpiring department told AFL.com.au the umpire had informed Cameron that the actual mark was still half a metre in front of where he was currently standing.

"We don't think it's a 50," the spokesperson said. 

"It is a reset at best. All Cameron tries to do is get away from Grigg, who tries to put a block on him.

"What should have been done at best is to have stopped play and asked Grigg to move out of the area."

There have been suggestions by several football commentators that Cameron infringed on the mark as he failed to move along the 'east-west' line. 

However, the AFL umpiring department has confirmed the rules state that players manning the mark in their defensive third of the ground are not restricted to moving laterally along the mark, and can move on an angle.