What should the ref do when a player comes off the bench and denies an obvious goal scoring opportunity?
Answer (October 1, 2012):
Send him off for denying the obvious goalscoring opportunity. It’s in the Law. Restart with an indirect free kick for the opposing team from the position of the ball when play was stopped (see Law 13 — Position of Free Kick). Indirect free kick is for the offense of unsporting behavior (sub enters without permission). The caution could be shown first, before the red card for denying the opportunity, but that might be overkill.