A measure adopted by a Union institution, even if it does not infringe any relevant rule of law, can still constitute an instance of maladministration if it is not in accordance with a principle that is binding upon the institution. This is a consequence of the definition of the notion of 'maladministration' that has been adopted by the Ombudsman and approved by the European Parliament. This definition provides that the yardstick to be applied covers not only rules, but also principles which are binding on an institution. It follows that just because there is no specific Community rule regarding restrictions of access to the Council building, this does not exclude the possibility that imposing such restrictions could amount to an instance of maladministration.