Each situation is different and it also depends on the patience and opinion of the referee. However, if a coach enters the field of play without permission, he should be warned by the referee (yellow card). Coaches are not shown yellow cards in US Youth Soccer matches so it is difficult to know if they have been warned from the sidelines. Once the coach enters the field and is warned, if he then "disagrees" with the referee, that could be considered dissent (yellow card) and thus his second caution and ejection. A referee could choose to ignore both instances, or penalize both.