A referee supervises a game of association football having full authority to enforce the Laws of the Game.
Decisions made regarding facts connected with play are final. The referee is assisted by two assistant referees (formerly known as linesmen), and in some matches also by a fourth official. The match officials utilise a positioning system known as the diagonal system of control. UEFA have also trialled the use of additional assistant referees who have jurisdiction over the goal areas and help interpret incidents in the immediate goal area or if the ball has crossed the goal line in the act of scoring a goal.
The vast majority of referees are amateur, though they are usually paid a small fee and/or expenses for their services. However, in some countries a limited number of referees – who mainly officiate in their country's top league – are employed full-time by their national associations and receive a retainer at the start of every season plus match fees.
Referees are licensed and trained by the same national organisations that are members of FIFA. Each national organisation recommends its top officials to FIFA to have the additional honour of being included on the FIFA International Referees List. International games between national teams require FIFA officials. Otherwise, the local national organisation determines the manner of training, ranking and advancement of officials from the youngest youth games through professional matches.
The referee's powers and duties are described by Law 5 of the Laws of the Game. These include: