The nature of the activity in or the physical location of the port can lead to the development of de facto monopolies with substantial entry barriers (for example, rarity of sites, need for public investment, or an insufficient level of activity for more than one operator). This type of situation makes the intervention of a regulating authority necessary to protect users from an abusive advantage due to a dominant position. However, this recognized need for oversight should not cast doubt on the principle of legal security, and must avoid any malpractice whereby the port operator could be subjected to arbitrary decisions.