<Li> Any part of the player's head, body or feet is closer to the opponents' goal line than both the ball and the second - last opponent . </Li> <P> (The goalkeeper counts as an opponent in the second condition, but it is not necessary that the last opponent be the goalkeeper .) </P> <P> A player in an offside position at the moment the ball is touched or played by a teammate is only penalised for committing an offside offence if, in the opinion of the referee, they become involved in active play by: </P> <Dl> <Dt> Interfering with play </Dt> <Dd> "playing or touching the ball passed or touched by a team - mate" </Dd> <Dt> Interfering with an opponent </Dt> <Dd> "preventing an opponent from playing or being able to play the ball by clearly obstructing the opponent's line of vision or </Dd> <Dd> challenging an opponent for the ball or </Dd> <Dd> clearly attempting to play a ball which is close to them when this action impacts on an opponent or </Dd> <Dd> making an obvious action which clearly impacts on the ability of an opponent to play the ball" </Dd> <Dt> Gaining an advantage by playing the ball or interfering with an opponent when it has </Dt> <Dd> "- rebounded or been deflected off the goalpost, crossbar, match official or an opponent </Dd> <Dd> - been deliberately saved by any opponent" </Dd> </Dl>

When was the offside rule introduced to football