From USSSA, (May 7, 2008 edition), page 21
Sec 5. SUBSTITUTE - A player who replaces a player that is in the game (offense or defense).
Teams are required to immediately report all substitutions to the Plate Umpire. Upon
notification by either team, the Umpire shall announce the legal substitute and make the
appropriate lineup card changes. An unreported legal substitute brought to the Umpire?s
attention will result in a penalty, all prior play shall stand.
PENALTY: For unreported substitution,
First offense: A team warning is issued.
Second offense: The head coach is ejected for the remainder of the game only.
A substitute or player who replaces a pitcher while the team is on defense shall pitch to
the first opponent to bat against the substitute until that batter has advanced to first base,
or has been put out or until there has been a third out. To ensure that the requirements
are fulfilled, the Umpire will deny any coach-defensive player conference that will violate
it.
A. If the starting pitcher is replaced before the first opposing batter has been put out or
advanced to first base, the pitcher may play or re-enter at another position, but shall
not return to pitch.
B. A player may be removed as a pitcher and returned as a pitcher only once per inning.
Provided the return as a pitcher does not violate either the pitching, substitution, or
charged conference rule. If the pitcher, because of injury or being incapacitated, is
replaced as pitcher and the above rule is not satisfied; or if the pitcher?s substitute
requires more warm-up throws than permitted, the pitcher shall not return to the
game as a pitcher.