LEED is a building design rating system created by USGBC to class a building that is designed to the LEED rating system. You do not need to be a LEED Accredited Professional to design or administer the LEED certification system for a LEED registered building. However, some employers would prefer its staff to become a LEED AP to show they and their staff have the fundamental understanding and are committed to green/sustainable design issues which is the underlaying driver LEED certification system.
However, some people would argue if LEED is nothing more then a rating system designed to chase points for the plaque on the wall since all of the fundamental principle of green/sustainable issues can be addressed without using LEED certification system.