I wrote the below on a different forum, as a way of trying to look at how the law is written and how it should be applied in this instance.
If we look at the law in detail. Gaining an advantage is defined as ...
• gaining an advantage by playing the ball or interfering with an opponent when it has:
•• rebounded or been deflected off the goalpost, crossbar, match official or an opponent
••been deliberately saved by any opponent
It hasn't rebounded or deflected off of any of those things, and it cannot be classed as a save due to the distance from goal. So as far as the law is concerned he didn't gain an advantage. Some have said that he interfered with an opponent, so if we look at that ...
• 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
Kane didn't do any of those things, so that rules out interfering with an opponent. The next paragraph is the most telling in terms of this decision, as follows ...
A player in an offside position receiving the ball from an opponent who deliberately plays the ball (except from a deliberate save by any opponent) is not considered to have gained an advantage.
Lovren deliberately played the ball. It can't be classed as a save as that is defined as "a ball that is going into or very close to the goal", so the law is clear that Kane cannot have been considered to have gained an advantage.