Pitch counter - not allowed

[efllblue]

I was watching an 11-12 LL All-Star game last evening and when the 1st base coach (kid) came out to the field with a pitch counter in hand, the 1st base ump made him return it to the dugout.

My questions are:
- Where in the rule book does it state that a base coach cannot have a pitch counter, or maybe is it any "foreign" object?
- Would it have made a difference if the coach would have been an adult?

Thanks...

-Scott