Law 11: Offside

Offside (sometimes known as offsides) is Law 11 in association football which states that if a player is in an offside position (as defined below) when the ball is touched or played by a team-mate, the player may not become actively involved in the play. A player is in an offside position when closer to the opponent's goal line than both the ball and the second-to-last defender (which is usually the last outfield player), and also in the opponent's half of the pitch. "Offside position" is a matter of fact, whereas committing an "offside offence" occurs when a player is "actively involved" and is subject to the interpretation of the referee. Goals scored after committing an offside offence are nullified if caught by the referee.

Application

The application of the offside rule may be considered in three steps: offside position, offside offence and offside sanction.

Offside position

A player is in an offside position if three conditions are met: first, the player must be in the opposing team's half of the field. Second, the player must be in front of the ball. And third, there must be fewer than two opposing players between him and the opposing goal line, with the goalkeeper counting as an opposing player for these purposes. It is not necessary that the goalkeeper be one of the last two opponents. Any attacker that is level with or behind the ball is not in an offside position and may never be sanctioned for an offside offence. IFAB has clarified in the 2009–2010 Laws of the Game that a player temporarily off the field of play is considered to be ON the boundary line at the point that he crossed over the boundary line. The 2005 edition of the Laws of the Game included a new International Football Association Board decision that stated being "nearer to an opponent's goal line" meant that "any part of his head, body or feet is nearer to his opponents' goal line than both the ball and the second-last opponent (the last opponent typically being the goalkeeper)." This is taken to mean that any part of the attacking player named in this decision has to be past the part of the second-last defender closest to his goal line and past the part of the ball closest to the defenders' goal line. (The hands are not part of the body).
Regardless of position, there is no offside offence if a player receives the ball directly from a corner kick, goal kick, or throw-in. However, an offside offence may occur if a player receives the ball directly from either a direct free kick or an indirect free kick.

Offside offence

A player in an offside position at the moment the ball is touched or played by a teammate is only committing an offside offence if, in the opinion of the referee, he becomes actively involved in play by:

Interfering with play

playing or touching the ball passed or touched by a team-mate

Interfering with an opponent

preventing an opponent from playing or being able to play the ball by clearly obstructing the opponent’s line of vision or movements or making a gesture or movement which, in the opinion of the referee, deceives or distracts an opponent.

Gaining an advantage by being in an offside position

playing a ball that rebounds to him off a goalpost or the crossbar having been in an offside position or playing a ball that rebounds to him off an opponent having been in an offside position.

Since offside is judged at the time the ball is touched or played by a teammate, not when the player receives the ball, it is possible for a player to receive the ball significantly past the second-to-last defender, or even the last defender (typically the goalkeeper).
Determining whether a player is in "active play" can be complex. The famous quote: "If you're not interfering with play, what are you doing on the pitch?", has been attributed variously to Danny Blanchflower, Brian Clough, and Bill Shankly. FIFA issued new guidelines for interpreting the offside law in 2003 and these were incorporated in Law XI in July 2005. The new wording seeks to define the three cases more precisely, but controversy regarding offside decisions often arises from assessment of what movements a player in an offside position can make without interfering with an opponent.

Offside sanction

The restart for an offside sanction is an indirect free kick for the opponent at the place where the off-sided player was at the time the teammate passed or touched the ball. This is defined as where the infringement took place.

Officiating

In enforcing this rule, the referee depends greatly on an assistant referee, who generally keeps in line with the second-to-last defender, the ball, or the halfway line, whichever is closer to the goal line of their relevant end. An assistant referee signals that an offside offence has occurred by first raising their flag upright without movement and then, when acknowledged by the referee, by raising their flag in a manner that signifies the location of the offence:

• Flag pointed at a 45-degree angle downwards: offence has occurred in the third of the pitch nearest to the assistant referee;
• Flag parallel to the ground: offence has occurred in the middle third of the pitch;
• Flag pointed at a 45-degree angle upwards: offence has occurred in the third of the pitch furthest from the assistant referee.

The assistant referees' task with regard to offside can be difficult, as they need to keep up with attacks and counter-attacks, consider which players are in an offside position when the ball is played, and then determine whether and when the offside-positioned players become involved in active play. The risk of false judgement is further increased by the foreshortening effect, which occurs when the distance between the attacking player and the assistant referee is significantly different from the distance to the defending player, and the assistant referee is not directly in line with the defender. The difficulty of offside officiating is often underestimated by spectators. Trying to judge if a player is level with an opponent at the moment the ball is kicked is not easy: if an attacker and a defender are running in opposite directions, they can be two metres apart in a tenth of a second.
Some researchers believe that offside officiating errors are "optically inevitable". It has been argued that human beings and technological media are incapable of accurately detecting an offside position quickly enough to make a timely decision. Sometimes it simply is not possible to keep all the relevant players in the visual field at once. There have been some proposals for automated enforcement of the offside rule.