Offside in rugby is a much simpler creature than it’s football counterpart with all its’ curious and enigmatic qualities. Ostensibly a player is offside whenever he is ahead of the ‘gain line’ (an imaginary line that goes from touchline to touchline in line with the ball). In other words, a player cannot receive a pass if he is in front of the player passing the ball. This means that even if the pass is not forward, you cannot come back from being in front of the passer in order to receive it. Similarly you cannot catch a kick from your own team if you are in front of your team-mate as they kick it.
This is most noticeable when teams are kicking for territory. Often you will see a team clear the ball out of their end of the field in order to alleviate pressure and if they fail to find touch, the opposition will quickly kick it back to keep the pressure on. It will appear that a lot of the team are just standing around watching things happen, but the reality of the situation is that they are unable to make a play on the ball because they are offside and must instead position themselves for play after someone else has touched the ball, thus playing them onside. The offside rule varies slightly when it comes to scrums, rucks and mauls as the off side line is judged by the position of the foot of the player at the rear of the scrum/ruck/maul. If a player joins the scrum/ruck/maul from in front of that foot then he will be deemed to be offside. The punishment for offside is usually a scrum unless the referee judges the player to have been ‘intentionally offside’ in which case the punishment is a penalty. Intentional offside is when a player commits an offence on purpose in order to gain an advantage or simply stop the opposition taking advantage of a situation.