Drawing the baselines (International Law of the Sea)

  • Normal baselines. The normal baseline is the low-water line along the coast
  • Straight baselines: a system of straight lines joining specified or discrete points on the low-water line, usually known as straight baseline turning points, which may be used only in localities where the coastline is deeply indented and cut into, or if there is a fringe of islands along the coast in its immediate vicinity. This method consists of selecting appropriate points on the low- water mark and drawing straight lines between them. Limits: i) the drawing of baselines must not depart to any appreciable extent from the general direction of the coast as it is the land which confers upon the coastal State a right to the waters off its coasts; ii) certain sea areas lying within these lines are sufficiently closely linked to the land domain to be subject to the regime of internal waters; iii) certain economic interests peculiar to a region, the reality and importance whicha are clearly evidenced by long usage, should be taken into consideration.


Specific rules + combined with the rules above-mentioned:

  • Bays: only applicable to normal baselines system
    • Bay bordered by a single State.
      • Juridical bays: Semi-circle whose diameter is a line drawn across the mouth of that indentation. For the purpose of measurement, the area of an indentation is that lying between the low-water mark around the shore o the indentation and a line joining the low-water mark of its natural entrance points. If there is an island across the mouth of the bay, it will be counted as 12 &12 nm.
      • Historical bays.
    • Bays bordered by more than one State: alternatives:
      • Bilateral agreement: the coastal State share internal waters.
      • Normal baselines system must be applied.


  • River: across the mouth of the river (it does not matter if there is a single riparian State or two riparian States). Applicable to normal baselines system as well as the straight baselines system.


  • Port: permanent harbour works. Installations and artificial islands must not be considered as permanent harbour works. Applicable to normal baselines system as well as the straight baselines system.


  • Islands: is a naturally-formed are of land, surrounded by water, which is above water at high tide. Exception: rocks which cannot sustain human habitation or economic life of their own shall have no exclusive economic zone or continental shelf.


  • Low-tide elevation is a naturally formed are of land which is surrounded by and above water at low tide but submerged at high tide.


*** Archipelagic waters: the right of innocent passage + the right of archipelagic sea lanes passage.




  1. Lighthouse: it is relevant. Above-water.
  2. Low-tide elevation on an island: irrelevant. It is necessary to pick up parts of the island that are above-water.
  3. Artificial island: irrelevant for delimiting baselines.
  4. Port: relevant. It consists of permanent harbour works.
  5. Roadstead: not relevant for drawing baselines, but they are included in the Territorial Sea in accordance with art. 12 LOSC: «Roadsteads which are normally used for the loading uploading and anchoring of ships, and which would otherwise be situated wholly or partly outside the outer limit of the territorial sea, are included in the territorial sea»
  6. Harbour works: only relevant if they are permanent.
  7. Reefs: not relevant for drawing baselines, but they are included in the Territorial Sea in accordance with art. 6 LOSC: «In the case of islands situated on atolls or of islands having fringing reefs, the baselines for measuring the breadth of the territorial sea is the seaward low-water line of the reef, as shown by the appropriate symbol on charts officially recognized by the coastal State»
  8. River: the line must be drawn across the mouth. Applicable to normal + straight baselines systems.
  9. Island: look for the low-water mark.



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