The FIFA “Interpretations of the Laws of the Game and Guidelines for Referees”, under the heading “Use of Whistle” on page 76, states:
The whistle is needed to: …
– restart play after it has been stopped due to: …
But, the July 2008 USSF “Guide to Procedures”, under the heading “Substitutions” on page 40, states:
[The referee] indicates that the restart will be delayed for the substitution and cannot occur except by the referee’s signal (whistle only if necessary)
So, does a substitution require a whistle for restart, or not?
USSF answer (March 24, 2009):
The whistle is required for all ceremonial restarts (every PK and KO, plus any other restart which the referee has delayed for any reason). We also missed changing it completely in the 2008 edition of the Advice to Referees. We will adjust to the instructions of the IFAB and FIFA. Draft editions of both books for 2009 include the changes made in the Interpretations in the 2008/2009 Laws of the Game.