Too Many PLayers on Field
 

HighSchool:

So a team can play with 8 on the field, but not 10. Before each inning i always do a quick could to make sure there are 8 or 9 on the field. My question is, what happens if i could 10? Is it my job to bring that up, as the umpire, or do i let it play until the offense complains? if they do , what is the penalty? is that an illegal substitution and the 10th player is restricted to dugout for the game? how can i be illegal substitution if he never really sub'd for a player? :)

I do a lot of little league (13 and under) and these crazy situations come up all the time, and i was just wondering the correct course of action.

Nip it in the bud, if possible. Otherwise, apply the rule.

3-3-1 . . . A coach, player, substitute, attendant or other bench personnel shall not: a. leave the dugout during a live ball for an unauthorized purpose...

PENALTY: At the end of playing action, the umpire shall issue a warning to the coach of the team involved and the next offender on that team shall be ejected.

Little League?
"Hey, coach, you've got an extra player out here"

That rule says "during a live ball" - it says nothing about dead ball situations, which this scenario is.

Yes, it's your job to find it, and to correct it. No other penalty.

If you discover it after a play, it's "not covered by rule" so you get to do what's right. I'd do something like let the offense keep any advantage, but nullify any play made by the defense.