One of the most famous works in the history of international law is Hugo Grotius' Mare Liberum from the beginning of the 17th Century. The entire discipline of international law is arguably founded on this, and dissertations like it, dealing with the legal peculiarities regarding situations with vessels from different countries on the high seas. “Mare Liberum” is literally “Free Sea” in English, that is, an area outside the territory of any state and thereby free from states' jurisdiction, and Grotius believed the high seas were just that. States begged to differ, naturally, and through the years they tried to extend their territorial sovereignty from land as far as possible in to the seas and oceans. In the 20th Century the technological advances that made the exploitation of the natural resources of the seas and the ocean floor much more efficient only increased the coastal states' desire to gain absolute control.
The situation needed regulating, and so far, the most significant word in the delimitation of maritime zones was written in 1982 when, after nine long years of deliberation, the United Nations Convention on the Law of the Sea (CLS) was finally (almost) complete. This convention is by many considered a constitution of the law of the sea. The convention's definition of the different maritime zones is the most extensive in any one treaty.
The baselines are the starting point from where all other zones are measured. These are usually the low water line along the coasts. There is a tradition of using straight lines across fjords and bays, but there are no established standards for this practice. Also, archipelagos may draw straight lines joining the outermost islands, within reason.
The internal waters
The internal waters lies between the baseline and the coastline. This includes rivers and their mouths, canals and harbors, and of course lakes. When straight baselines have been used, quite considerable areas of water close to a state may be internal waters (especially in the case of archipelagic waters). Internal waters is treated like land territory and the coastal state has complete jurisdiction and absolute territorial sovereignty.
The territorial sea
Extending outwards from the baseline is the territorial waters. In the old days, the breadth of this belt was as long as a cannonball could reach, fired from the shore. In the 19th Century 3–4 nautical miles was one norm, but many countries extended on this for reasons of economy (fishing) or national security. The CLS set the maximum range to 12 mi. As was the case with a coastal state's internal waters, terriotorial sea is treated like land territory, but with the exception that foreign vessels (ships, not airplanes) have the right to “innocent passage”, that is, peaceful navigation through the waters. Such passage must be “continuous and expedititious” and submarines must remain surfaced.
The right to innocent passage, as given by the CLS, includes some protection from the jurisdiction of the coastal state, and only if the following conditions are met can the crew be arrested or the ship inspected:
- “if the consequences of the crime extend to the coastal State;
- if the crime is of a kind to disturb the peace of the country or the good order of the territorial sea;
- if the assistance of the local authorities has been requested by the master of the ship or by diplomatic agent or consular officer of the flag State; or
- if such measures are necessary for the suppression of illicit traffic in narcotic drugs or psychothropic substances”
Whether warships can claim innocent passage is contested. United States believe they can, China believe they can't.
Special rules govern international straits such as those of Dover, Hormuz or Gibraltar. For these straits vessels' rights to safe passage are reinforced. And not only does the right to transit passage unambigiously cover warships (even submarines may remain submerged) it also covers airplanes as this was a condition for several states before agreeing to a 12 mi territorial belt. Some straits (e.g. Bosporus) have individual treaties governing their use. As do man-made canals like Suez and Panama.
The high seas
If an area is outside both the territorial or internal waters of any coastal state and its exclusive economic zone (see below) it is considered high sea. The high seas are fundamentally free, and the vessels travel only under the jurisdiction of their flag state. The freedom of the high seas comprises
- freedom of navigation
- freedom of overflight
- freedom to lay submarine cables and pipelines…
- freedom to construct artificial islands and other installations permitted under international law…
- freedom of fishing…
- freedom of scientific resarch…
The list is from the CLS, slightly truncated as it refers to articles of further regulation of these areas in the convention, but the basic principle remains that any state (coastal or inland) and its vessels are free to do as they please on the high seas as long as they do it peacefully and without restricting other states in doing the same.
The one major exception to these rules is piracy and slave trade. Pirates and slave traders is under the jurisdiction of any nation, and warships may board such vessels. Near coastal waters, there might be a few further restrictions on the freedom of the high seas, as described below:
The contiguous zone
The contiguous zone borders the territorial seas of a coastal state and extends no longer than 24 mi from the baselines. While it is technically in the high seas, the zone gives the coastal state jurisdiciton in cases concerning immigration, sanitation, taxes or customs if the crimes have been committed inside the territory of the coastal state. Thus, the contiguous zone gives states a better chance to catch fleeing vessels. Even if the culprit manages to escape from the contiguous zone the coastal state may continue the chase if it is engaged in “hot pursuit” and this chase is not interrupted. If the culprit sails into another state's territorial waters the chase has to be called off, hot pursuit or not.
The exclusive economic zone (EEZ)
Since the 1960es coastal states have laid claim to special fishing zones exclusive to those states. Acceptance of such claims conflict with the freedom of the seas, but it became customary to accept exclusive fishing zones to an extent of 12 mi from the baselines, nonetheless. This escalated into claims of what was now known as exclusive economic zones to an extent of up to 200 mi from the baselines, and these claims were eventually accepted as well.
In the EEZ, the states have
“sovereign rights for the purpose of exploring and exploiting, conserving and managing the natural resources, whether living or non-living, of the waters superjacent to the sea-bed and of the sea-bed and its subsoil, and with regard to other activities for the economic exploitation and exploration of the zone, such as the production of energy from the water, currents and winds”
The coastal state is also given the jurisdiction to uphold these rights. In all other aspects, the rules and freedoms of the high seas prevail.
The continental shelf
This is the seabed and subsoil to the extent of no less than 200 mi from the baselines (which makes the area co-extensive with the EEZ) and up to 350 mi, or, alternatively, up to 100 mi from the 2.5 kilometers isobath. If a coastal state lays claim to the continental shelf in extent of over 200 mi they have to pay an annual fee to the International Seabed Authority.  In this area the coastal state has sovereign rights to explore and exploit the natural resources of the sea-bed and subsoil, not the sea above it (unless, of course, the sea above it is in the coastal state's EEZ).
The sea-bed and ocean floor and subsoil thereof
This area has been the most controversial. In 1970 the United Nation's General Assembly announced that “The sea-bed and ocean-floor, and the subsoul thereof, beyond the limits of national jurisdiction (hereinafter referred to the area), as well as the resources of the area, are the common heritage of mankind.” The idea was that third world states and, explicitly, “mankind as a whole” should be given an opportunity to take part in the exploitation of the natural resources of the sea. In the convention of 1982 this was the last unresolved issue. The idea was to give all rights to this, the area, to the International Seabed Authority (ISA). The ISA would then either exploit it themselves or sell concessions. This was unacceptable to most industrial countries and many of them (notably United States and the Soviet Union) instead created national laws governing authorizations to exploit the area. However, ultimately nobody was interested in the costly exploitation of the area, and in 1994 a compromise was reached that liberalized the acces to the area while retaining the system of licenses and fees to the ISA.
(This is part of my personal quest (study) on international and humanitarian law)