Player counts out loud

[JetMetFan]

Originally Posted by DenverRef

While the referee administers the throw-in to A1, B2 begins the 5 second count OUT LOUD to his teammates who are pressing. His count differs from referee's.

What do you have?

I warned the player and the coach about it and the player did stop doing it after that. But then I was wondering if it was legal? I can't find it in the rulebook.

Something like this isn't specifically covered under Rule 10 in the NFHS or NCAA codes but Rule 2-3 in both is the "Elastic Clause" which allows the referee to make decisions on any points not specifically covered in the rules. If you felt it was unsporting - which it seems you did - you could have given the defender a technical foul but warning him first made sense.