Every day is a day of learning, thanks all. ICAO Annex 2,
Restricted area. An airspace of defined dimensions, above the land areas or territorial waters of a State, within which the A flight of aircraft is restricted in accordance with certain specified conditions.
“3.3.2.2 According to their definitions, a danger area implies the least degree of restriction, while the prohibited area constitutes its most stringent form. It should also be noted, however, that this definition is applied only with respect to airspace which is situated over the territory of a State. In areas where no sovereign rights are exercised (e.g. over the high seas) only danger areas may be established by that body responsible for the activities causing their establishment.”
“3.3.2.4 Over the high seas, regardless of the risk involved, only danger areas can be established. Those who initiate danger area restrictions over the high seas are under an increased moral obligation to judge whether establishment of the danger area is unavoidable and if it is, to give full details on the intended activities therein. It would also appear that activities exceeding a certain risk level should not be conducted in such airspace and that other methods of achieving the desired objective, such as temporary airspace reservations, should be applied.”