HOA Homefront: How exclusive is an exclusive-use area? (Part 2)

The following column is part 2 in a series on exclusive-use areas in HOAs. Part 1: What, where is an “exclusive use common area?” 
Q: I live in a condo complex in which the restricted common area includes the front and backyards of each unit. The board says it has the authority to grant permission to an owner to make room additions in the backyard. I do not believe they have such authority as it would be “giving” ownership of the restricted common area which would th