Question:
Is it true that there are only three cautions that can be given to a player on the bench? If that is true, is it true that entering the playing field without permission is not one of the three?
USSF answer (April 19, 2010):
Yes, it is true (see below). The substitute who enters the field without the permission of the referee is cautioned for unsporting behavior.
Disciplinary Sanctions
The yellow card is used to communicate that a player, substitute or substituted player has been cautioned.
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A substitute or substituted player is cautioned if he commits any of the following three offenses:
* unsporting behavior
* dissent by word or action
* delaying the restart of play
You will find the notice about cautioning a substitute for entering illegally in the 2008 supplemental memorandum on law changes:
Law 12
The International Board has reconfirmed this year, by making no change in the list of reasons for which a substitute or substituted player may be cautioned, that a substitute or substituted player who illegally enters the field is to be cautioned for unsporting behavior. Law 12 The International Board has reconfirmed this year, by making no change in the list of reasons for which a substitute or substituted player may be cautioned, that a substitute or substituted player who illegally enters the field is to be cautioned for unsporting behavior.
. . . and in the Advice to Referees, Advice 12.28.1.