http://www.thefa.com/football-rules-governance/lawsandrules/laws/football-11-11/law-11---offside
Well there it is, the good old Offside Rule in its current guise.
Ref; The Cav / Dicko Incident.....part of the above link refers to the following :-
"Offside Offence
A player in an offside position at the moment the ball is played or touched by a team-mate is only penalised on becoming involved in active play by:
interfering with play by playing or touching a ball passed or touched by a team-mate or
interfering with an opponent by:
preventing an opponent from playing or being able to play the ball by clearly obstructing the opponent’s line of vision or
challenging an opponent for the ball or
clearly attempting to play a ball which is close to him when this action impacts on an opponent or
making an obvious action which clearly impacts on the ability of an opponent to play the ball"
Reading through the 'rules of the game', many of them start with, "If, in the opinion of the Referee...."
I can only assume that on this occasion, the linesman thought Cav was interfering with play, but with the above in mind I'm not sure how ?
This is the problem, some will have flagged yesterday, some wouldn't, so there is no consistency.
I would rather go back to the way things were years ago. If you are in offside position, regardless of whether or not you are interfering with play, you are Offside, and that's it. That way nothing is open to interpretation, everyone knows where they stand and every linesmen will have an easy decision to make without any of that Phase 1, Phase 2 nonsense.