Can an employee be banned from a store for posting pictures of himself and his fellow workers on Facebook?

I work at EB Games. About a week and a half ago a fellow employee and I got suspended from work and BANNED from the store for posting pictures of us and the other workers on Facebook. We never revealed or slandered the name of "EB Games" in any of the photos. Just recently my fellow employee got fired. Is all this legal? Especially the banned from the store part?