Little League International has written the following:
Until we receive your response, we are encouraging parents and coaches to contact manufacturers directly to verify if their players’ helmets will retain their NOCSAE certification, and, that they must produce that notice from you, the manufacturer, prior to use in any and all Little League-related activity. Without manufacturer- approval, Little League International will follow the advisement that “the addition of such products to a helmet previously certified as meeting the appropriate NOCSAE standard will make the certification voidable by the helmet manufacturer,” and helmets with a face protector will not be permitted for Little League-use. Little League International will encourage anyone wishing to have additional face protection to use a helmet with a full faceguard that is NOCSAE certified.
Click on the story subject for the full PDF document regarding face protectors like the c-flap, etc.