Just noticed a flaw: free kicks.
So:
If, while the ball is in the field of play* and you are in your opponents half, ahead of the ball, and there are fewer than two opposing players between you and their goal-line, you are offside if you interfere with play when the ball is kicked by a team...
It has happened at free kicks, with an opposing player standing in the keeper's eye-line. Technically it should be offside, but I don't know if it is always given partly because "interfering with play" is something the linesman has to judge and sometimes he might not have the best perspective to...
Not any more:
Offside position
It is not an offence in itself to be in an offside position.
A player is in an offside position if:
• he is nearer to his opponents’ goal line than both the ball and the
second-last opponent
A player is not in an offside position if:
• he is in his own half...
The law no longer specifies that the ball be played to the person interfering with play, so the ball wouldn't need to be passed to Barnes for him to be considered interfering with play, so I think it would be, and if the linesman didn't flag, I would presume the ref would blow for ungentlemanly...
If, while the ball is in play, you are ahead of the ball, in your opponents half, and there are fewer than two opposing players between you and the goal-line, you are offside if you interfere with play when the ball is kicked by a team mate.