Enacting and developing international environmental law - Introduction to International Environmental Law - page 69

and virtually uniform and it shall have prevailed for a certain time. States should
also feel that they are observing a practice because they are obliged to do so by
a legal rule. In contrast, other customs and ceremonies are observed in many
areas of international cooperation, although not because states consider them
legally binding. 18
The development of customary law
The rights of coastal states to the continental shelf provide a good example of
the development of customary law.
When the United States, as one of the victors of the Second World War,
issued the Truman Proclamation in 1945 stating that it had control of the
natural resources of the seabed in areas adjacent to its coastline, other
coastal states progressively followed the example. In time, this resulted in
all coastal states having the continental shelf as a customary law entitlement.
The right of coastal states to the natural resources of their continental
shelves was recorded in the 1958 Convention on the Continental Shelf, 19
although the outermost limits of the continental shelf were not defi ned
until 1982 when the UN Convention on the Law of the Sea 20 was adopted.
A similar 'traditional' progress of customary international law resulted from
the USA's provocation of Canada in 1969.
The United States considered (and still does) the Northwest Passage to be an
international strait free for all the world's ships to cross. In 1969, the USA sent
an ice-strengthened oil tanker, the SS Manhattan , to cross the Northwest
Passage, which created an enormous stir in Canada. As Canada did not consider
the Northwest Passage to be an international strait, but Canadian internal waters,
the action of the US was considered to be a violation of Canadian sovereignty.
Canada reacted by enacting the Arctic Waters Pollution Prevention Act in
1970, 21 according to which it assumed the right to control all vessels entering
the ice-covered Northwest Passage, ostensibly to protect the vulnerable Arctic
environment. Canada went so far as to justify its action based on its purported
responsibility to humanity. This policy contradicted the international law of
the sea, which at the time only allowed very limited intervention in seafaring
beyond territorial waters.
Sometimes customary international law can only progress through violation
of an existing customary law rule. Canada was active during the negotiations
for the UN Convention on the Law of the Sea (UNCLOS) in 1973-82, and
gained the acceptance of the international community for its action. Article 234
was written into the UNCLOS text, which guarantees all coastal states adja-
cent to ice-covered waters the right to control the movements of vessels more
closely than anywhere else within their exclusive economic zones (a radius of
370 kilometres, or 200 nautical miles from the coast). Because of the interplay
between treaty law and the evolution of customary international law, the
codifi cation of this provision in the UNCLOS has resulted in the evolution of
Article 234 into a rule of customary international law.