Offside
The provision as it is printed, and everything on Ruleside that turns on it.
An attacker in an offside position (A) runs towards the ball, preventing the opponent (B) from playing or being able to play the ball by challenging the opponent for the ball. (A) is challenging an opponent (B) for the ball.
Worked by IFAB itself 1
One of the positions the Laws answer by name rather than by rule, drawn.
The Laws of the Game are published by The IFAB and quoted here for the purpose of explaining the decisions on this site. Ruleside is not affiliated with The IFAB or FIFA. Every clause of Practical guidelines for match officials that Ruleside cites.