Observers are the closest Ultimate has to referees. Unlike referees in traditional sports, observers allow the players to to make their own calls and resolve them on their own. If there is a dispute that cannot be resolved between the players, one of the involved players may ask the observer for an observer ruling, which is final (except in rare circumstances). Players may also go to observers for rule clarification after making a call. An observers main priority are considered 'active calls,' and include in/out calls, off side calls on the pull, and time violations, including time between points, half, and time outs.
The majority of ultimate games are not observed; however, tournaments will often have championship games, as well as other important or closely contested matches.