What must happen if a referee uses a dual system of control and a third referee arrives?

When a referee is using a dual system of control and a third referee arrives, the proper procedure is to transition to a diagonal system. This method employs three officials on the field, which allows for better coverage of the game and improved officiating. The diagonal system facilitates effective oversight of the match by positioning the officials in a manner that enhances their ability to monitor player actions, maintain control, and adjudicate plays accurately.

The arrival of a third referee signifies that the game can benefit from the additional support and that the trio can function more efficiently using the diagonal system. Utilizing this strategy ensures that all areas of the field are given appropriate attention, and it aligns with standard officiating practices in soccer. The options to stop the game or continue with the dual system would not improve the quality of officiating, and having a fourth official specifically would not apply in this context as a third referee should immediately transition into a diagonal system with the other two referees.