Laying on the floor to head ball back - an offence or not?

In March on this blog, I asked if Chelsea's Ashley Cole should have been penalised after laying on the ground to head the ball back to his goalkeeper. The referee at the time took no action, despite Cole apparently abusing the spirit of Law 12, which says a player should be penalised with an indirect free kick and booked if he  ... "uses a deliberate trick while the ball is in play to pass the ball to his own goalkeeper with his head, chest, knee, etc. in order to circumvent the Law ...


Well yesterday, it was the turn of  Chelsea's David Luiz to do exactly the same and avoid punishment.  

Now we all know the goalkeeper cannot pick the ball up if it is kicked back to him but can if the head or chest is used or if the ball comes to him as a result of a slice or accident.
But fewer know that a player cannot use a trick to pass the ball back. So in general, flicking the ball onto your head and heading it back to the goalie should result in a yellow card for unsporting behaviour and an indirect free kick.
FIFA's advice to referees reads that a player must be cautioned if he "uses a deliberate trick while the ball is in play to pass the ball to his own goalkeeper with his head, chest, knee, etc. in order to circumvent the Law ... The offence is committed by the player in attempting to circumvent both the letter and the spirit of Law 12 and play is restarted with an indirect free kick."
Many referees argue that this was a trick, that he avoided what would have come naturally, i.e. kicking the ball back. Others say it's not an offence to head the ball back to the goalkeeper so Luiz didn't commit any offence.