MELBOURNE coach Paul Roos says the AFL has made it incredibly difficult for umpires to do their job.

Roos has been among the most vocal of many coaches to criticise this year's tougher interpretation of deliberate out of bounds and rushed behinds.

The former Sydney Swans mentor expressed frustration over "un-umpirable" rules earlier this year.

The out of bounds law hit the headlines after round 21, with umpires boss Hayden Kennedy ticking off a contentious call in the final minute of a Friday night thriller.

Western Bulldogs coach Luke Beveridge, speaking after his side's three-point win, suggested it was clearly not a free kick.

Roos feels whistle blowers have been pitched into an unfair position by the Laws of the Game committee.

"It's such a hard game to umpire. We probably have a set of rules and (a) set of guidelines," Roos said on Wednesday.

"So we don't actually have a full set of rules any more. Which is quite strange. 

"It's really up to the umpires to interpret those guidelines as best they possibly can.

"It does make it really, really difficult ... for them to be able to umpire the game."