Text Book decision. They should use that at ref school. Had a second defender been on the line then the goal would stand. Just a pity he got so much else wrong.
Could you explain it, Fez, please? Is it true the players not on the pitch are considered level on the goal-line?
That's exactly it. He went off the pitch as a matter of course in play. He hadn't deliberately left the field to gain an advantage. Offside, as a position (not a technical offence) is for an attacking player to be in the opposition half, in front of the ball, and behind the penultimate defender (level is onside). There's one WBA player on the goal line but the GK and all of the other defenders are two yards up the pitch. When the shot is taken Sema is in an offside position; when he becomes active (i.e. plays the ball) he is adjudged offside. Had a second defender been on the line as well then Sema would be "level" with the penultimate defender and defacto onside. It's a perfect example of how the law should be applied.