Rugby sevens uses the rugby union offside laws, with sevens variations affecting the surrounding restarts and set pieces. The central idea is simple: a player who is ahead of a team-mate who carries or last played the ball is in an offside position and must not use that position to affect play.
A player is offside in open play when that player is in front of a team-mate who is carrying the ball or who last played it. If the last action was a kick, the kicker's foot creates the offside line at the moment of the kick.
That position only becomes a problem when the player takes part in play while still offside. The player must avoid interfering, retreat when required, and wait to be put back onside before chasing, tackling, receiving, or blocking space.
There are only seven players per side, so one early runner can close a huge amount of space. A player who creeps ahead at a ruck, leaves a scrum early, or chases a kick from in front can turn a fair contest into an unfair one almost immediately.
That is why offside calls in sevens often look strict. The referee is protecting the space that the laws give the attacking team, the receiving team, or the team that has stayed onside.
An offside player in open play should stop affecting the game. The player must not play the ball, move toward the ball, tackle the ball-carrier, prevent opponents from playing as they wish, or loiter in a position that blocks options.
For example, a winger ahead of a team-mate's pass line is offside if the ball was last played by that team-mate behind them. If the winger stands still and gets out of the way, play may continue. If the winger catches the ball, shields a defender, or joins the next chase, the referee can penalise it.
The safest way for an offside player to fix the problem is to retreat behind the team-mate who last played the ball or behind another onside team-mate. In many open-play situations, an onside team-mate can also run past the offside player and put that player onside.
Some opponent actions can put an offside player onside, such as an opponent kicking the ball or intentionally touching it without gaining possession. Those opponent actions do not rescue every situation, especially the 10-metre law for kicks, so players are coached to retreat first instead of hoping the referee will consider them onside later.
Kick chases create many sevens offside decisions. A team-mate in front of the kicker is offside. If that player is within 10 metres of where the ball is caught or lands, the player must retire immediately behind an onside team-mate or behind the imaginary 10-metre line on that player's side of the landing point.
That player cannot simply wait for an opponent to catch the ball and then tackle. If several offside players are affected, the closest player to where the ball lands or is caught is usually the one the referee penalises.
The 10-metre kick law does not apply when the kick is charged down or touched in an attempted charge-down. That exception matters because the ball has not travelled as a normal tactical kick with a normal chase line.
A player who was in front of the original kicker still cannot use an illegal position to obstruct or play unfairly, but officials treat a charged-down kick differently from a clean kick downfield or a contestable restart.
At a ruck, each team has an offside line running parallel to the try lines through the hindmost point of any ruck participant on that team's side. Arriving players must join from behind that line or retire behind it immediately.
In sevens, rucks are often small and fast, but the offside line still exists as soon as a ruck forms. A defender who steps around the side, reaches from ahead of the hindmost point, or stands in the passing lane before the ball is out risks a penalty.
At a maul, the offside line for each team runs through the maul participants' hindmost foot nearest that team's own try line. Players must join from an onside position, bind legally, or retire behind the line.
A player who leaves a maul must also retire behind the offside line before rejoining or defending from open space. If the player simply detaches and blocks the ball-carrier or shuts down a pass from the side, the referee can treat it as offside or illegal maul entry.
A sevens scrum has three players from each team, and all three must stay bound until the scrum ends. Players who are not in the scrum must stay at least five metres behind the hindmost foot of their team until the scrum is over, unless they are the scrum-half in a legal scrum-half position.
The defending scrum-half has specific options around the scrum and cannot simply track ahead of the ball. Once the scrum ends, scrum offside lines no longer apply and normal open-play offside takes over.
Lineout participants must stay on their own side of the mark of touch and follow the lineout offside restrictions until the lineout legally ends. Players not taking part in the lineout must normally stay 10 metres back from the mark of touch on their own side, or behind their try line if that is closer.
The sevens variation makes lineouts form within 15 seconds once the mark is indicated, but it does not remove the lineout offside lines. Defenders cannot rush up early just because the throw is quick or the lineout is small.
For a halfway kick-off or restart, team-mates of the kicker must be behind the ball when it is kicked. In sevens, after a team scores, the scoring team restarts with a drop kick from halfway, so this offside line appears often.
If a team-mate starts in front of the ball at a sevens restart, the sanction is a free-kick to the non-offending team. If the player was behind the ball but then contests early or dangerously, the referee judges that separate action under the restart, offside, and foul play laws.
Most deliberate or material offside offences bring a penalty. For the main open-play offside offences in Law 10, the non-offending team may have a choice between a penalty at the place of infringement and a scrum where the offending team last played the ball.
Accidental offside is different. If a player cannot avoid being touched by the ball or by a team-mate carrying it, play only stops if the offending team gains an advantage, and the sanction is a scrum. Referees also apply advantage when the non-offending team is better served by play continuing.