Enacting and developing international environmental law - Introduction to International Environmental Law - page 71

States endeavour to control and prevent most environmental threats by inter-
national treaties. It is natural that states should want to expressly record the
rules and obligations they are prepared to undertake in order to control a given
environmental problem.
Customary international law is not an adequate tool for reacting to environ-
mental threats because it is often open to interpretation. 22 Environmental
threats should be addressed at the earliest possible stage and managed in a way
that is fl exible and able to adapt to the latest scientifi c research.
One advantage of customary international law is that it binds every nation
in the world, whereas conventions bind only the parties to them: so, for
example, if 150 states are parties to a global convention, more than 40 states
remain outside the regime. If it can be proven and verifi ed that most of the
convention rules have evolved into customary international law, the rules will
be legally binding to all the states of the world. Even if a state withdrew from
the treaty in question, it would still remain legally bound by the customary
international law. 23
This difference remains highly relevant, particularly because the USA, for
example, has deliberately remained outside of many global and regional inter-
national environmental agreements. It is not a party to the UNCLOS, and
therefore not directly bound by the provisions of Part XII of the Convention
regulating the protection of the marine environment. Nevertheless, since
1982, Part XII has become accepted as customary international law, and its
provisions therefore are binding worldwide. The USA has endorsed these
rules as legally binding as a matter of customary international law.
On the other hand, some states have consistently objected to the status of
such principles as the precautionary principle as customary international law
and they are fully entitled to do so. If a state consistently objects to the evolu-
tion of a principle or rule into a principle of customary international law, the
principle does not apply to that state, even if the principle evolves into a
customary law principle that is binding to all other states. This is known as the
persistent objector doctrine.
The greatest problem in the development of customary law is often the fact
that it is diffi cult to say when a customary international law rule came into
being or 'crystallized' in the language of international lawyers. The legal status
of the principle of no-harm, for instance, has been unclear ever since an inter-
national arbitration tribunal was established to settle a dispute between the
USA and Canada concerning sulphur oxide emissions from a zinc and lead
smelter on the Canadian side, which had caused environmental damage in the
state of Washington, on the US west coast. In its decision in 1941, the arbitra-
tion tribunal stated that no country is entitled to use its territory, or permit it
to be used, in a way that causes damage to the territory of another country, its
inhabitants or their property.
It seems, then, that a rule of this type was established as early as 1941. The
problem remained that the arbitration tribunal did not, in fact, consider the