2009 OFFICIAL RULES & REGULATIONS, page 32

Rule 1.17-(d)  CATCHERS MUST WEAR A CATCHER'S MASK ATTACHED TO A HELMET AS DESCRIBED IN PARAGRAPHS 1.17-(a)-(c) ABOVE. A HARD PLASTIC PROTECTOR MANUFACTURED FOR THE PURPOSE OF PROTECTING THE THROAT SHALL BE SECURELY ATTACHED TO THE MASK EVEN IF THE MASK HAS AN EXTENSION AT THE BOTTOM.

This rule requires a throat guard attached to the catchers face mask at the bottom of the mask even if it has a built in extension.  This applies to all leagues that places a catcher behind home plate and all types of catchers mask (Hockey style or traditional).  Skull type helmets have been banned.