Legal responsibility for environmental damage - Introduction to International Environmental Law - page 170

Liability based on the principle of due diligence
Despite the long-term efforts of the International Law Commission (ILC) to
produce separate state responsibility rules to cover environmental damage,
state responsibility is still defi ned according to the general law of state respon-
sibility codifi ed by the Commission. These general rules only give rough
guidelines as to which rules are applicable should a state violate international
law - including international environmental law. They defi ne, inter alia , what
constitutes a violation of international law, what actions can be considered by
a state (as opposed to by a private individual or commercial entity), and how
states can lawfully respond to violations of international law committed by
other states.
The general rules of state responsibility codify customary international law
in many respects; many of them refl ect the existing general international law.
They operate in the same way as the customary law that applies to all treaties:
they apply, unless otherwise agreed by the states. The articles do not describe the
requirements from states in each case in detail - the so-called 'primary rules'
of international law. Instead, the articles focus only on what are called 'second-
ary rules': that is to say, the consequences of a state's violation of one or more
of the primary rules, of a state not doing what is expected of it. The position
of the ILC is that although the primary rules vary widely in different fi elds of
international law - including the standard of care that is expected of a state
(the degree of diligence due) - in the event that a primary rule is violated, the
same secondary rules apply.
The main rule in environmental law is that of legal responsibility based
on fault - or negligence. The 'mental' attitude to international law of an
individual official or state is unimportant; the first issue to be established
is whether, for instance, the principle of due diligence was violated:

• Can state B verify that the pollution damage incurred in its territory is due

to certain conduct on the territory or under the jurisdiction of state A?

When this causal connection is clear, the next step will be to fi nd out what
measures have been taken in relation to this action:

• Has state A permitted this project, and if so, on what terms?

• Has it examined the possibility of transboundary impacts in advance?

• Has it notified state B of these risks and arranged mutual negotiations?

There is no way of saying exactly when a state has done what is required in
terms of diligence in such cases. The higher the probability of serious trans-
boundary impacts, or the more severe the potential damage, the higher the
standard of care (diligence) required.
The principle of no-harm in customary law requires similar diligence in cases
where environmental damage can be caused to the environment beyond state