institutions. Generally speaking, a civil servant should always refrain from enunciating personal opinions in a manner that can be construed as expressing the official opinion of the French government or a public institution. Obviously, this is more of a matter for the higher managerial positions. Agents operating abroad should be especially prudent. For instance, an ambassador should refrain from making any private comment on international issues. The academic freedom of university professors is a principle recognized (in theory) by the laws of the Republic, as defined by the Constitutional Council; furthermore, statute law declares about higher education that "teachers-researchers [university professors and lecturers], researchers and teachers are fully independent and enjoy full freedom of speech in the course of their research and teaching activities, provided they respect, following university traditions and the dispositions of this code, principles of tolerance and objectivity". Hierarchical obedience A civil servant must accomplish the orders given by his hierarchical supervisor, unless those orders are evidently illegal and contrary to public interest. While the hierarchical authority is normally responsible for assigning civil servants to positions and evaluating their work, certain corps of civil servants follow specific rules regarding the management, evaluation and discipline of their members. For instance, professors and researchers are evaluated by elected committees of their peers. Furthermore, judges of the judiciary (magistrats du siège) as well as administrative magistrates cannot be removed from their position, even for a promotion, without their agreement. Professional discretion Civil servants must not reveal private or secret information that they have gained in the course of their duties. Depending on a civil servant's corps, this obligation may be of varying intensity : while administrative magistrates are formally discouraged from making their profession in non-professional works and opinions, members of the military are expected to maintain a very high standard of discretion. This restraint on the side of the military has even led it to being nicknamed "the great mute" ("la grande muette"). Honesty Civil servants must not use the means at their professional disposal for private gain. Neutrality Civil servant must be neutral with respect to the religious or political opinions, origin, or sex, and should refrain from expressing their own opinions. Recruitment and career Most positions are open to citizens of the European Union. Certain positions involving the main powers of the state (e.g. Police) are open only to French nationals. Some rare positions, e.g. university professors