Too many players on the field

There has been a big sporting controversy in Adelaide when one team in the Preliminary Final of the local Australian Rules Football competition started the 4th quarter with an extra player (18 players is the usual number, but they had 19 on the field). During the period they had the extra player, they scored 8 points, and eventually won the game by a margin of 5 points. After a hearing the result was allowed to stand, although they have penalised in other ways.
Interestingly, if they were using the Laws of Chess during the game, they may have been able to resolve it differently. Once the irregularity was observed, the umpires could have simply removed the points scored, reset the clock to the start of the quarter, and began again. Indeed this approach may have been better than what was decided (which I disagree with), or simply awarding the game to the opposition by removing the 8 points in question (which I thought should have been the decision).
Anyway, here is a related puzzle, concerning an extra man on the field. It is White to play and Mate in 1 move.