Freedom of navigation (FON) is a principle of law of the sea that ships flying the flag of any sovereign state shall not suffer interference from other states, apart from the exceptions provided for in international law. In the realm of international law, it has been defined as “freedom of movement for vessels, freedom to enter ports and to make use of plant and docks, to load and unload goods and to transport goods and passengers". This right is now also codified as Article 87(1)a of the 1982 United Nations Convention on the Law of the Sea. Not all UN member states have ratified the convention; notably, the United States has not signed nor ratified the convention. However, the enforces the practice; see below.