I officiated high school and college basketball for 37 years. I no longer do college, but still officiate high school basketball. High school rules do not allow for any jewelry to be worn by player or officials, except for a smooth wedding ring, (no stones), or a medical bracelet that must be taped to their wrist. No necklaces of any kind may be worn. If you have ever watched a basketball game and have seen several player s go up for a rebound, it is very possible for a hand or arm to be slipped through a necklace or any head scarf that could result in injury to both parties. The PIAA (Pennsylvania Interscholastic Athletic Association), which is the administration association for all state high schools in Pennsylvania, did write an exception a few years ago to allow Muslim girls to wear their head scarfs, (sorry, I do not know the proper word), during athletic contests, but the school must sign a letter of liability that if anyone should become injured due to the wearing of the head scarf, the school would assume all liability.
I know of a few incidents where officials were injured by players getting their hands stuck on an official's whistle lanyard and pulling the lanyard with enough force to put ligature marks around their necks and also causing injury.