Interface for determining if a object is restricted could be better

I'm currently using object.access_groups.count() to determine if access to 'object' is restricted. In other words, if an AccessGroup was added to the object then it is restricted. Would creating some static method on AccessGroup make the interface cleaner? For example, AccessGroup.is_restricted(object) would return a boolean and more importantly, if the object has an implied restriction due to some sort of relationship, is_restricted() would be able to determine it via the 'control_relation'.