What's the problem with the buckle on the Casablanca helmets?

If you are a USPA member, you will have received the notice below last week. The notice concerns the "magnetic buckles on certain NOCSAE-compliant helmets manufactured by Casablanca", and annouces a rule variance that allows players to play in non-compliant helmets while waiting to have the buckle replaced by Casablanca or a new helmet delivered.