I also had a BV player attempt to wear an ipod and a stocking cap during warmups earlier this season. I simply stopped him in the layup line and told him that he needed to go to the bench and remove those items right away.
There was no fuss at all. He simply did as necessary.
He was a nice kid and the team captain. He simply didn't know that he couldn't have that stuff on during warmups.
For rules support see the previous posts by JR and RD.
