Which of the relevant international environmental law principles have arguably reached
the status of customary international law and on what basis could one make that
conclusion? Select at least three international environmental law principles and critically
analyse them with a specific focus on tracing their development, outlining the basis upon
which it could be argued that they have attained customary law status and any views to
the contrary.
International environmental law is essentially a set of agreements, rules and principles that
reflects the international community’s cooperative efforts to conserve the environment and
reduce the negative human impact that we have created on the environment. As
environmental threats across the globe have increased, including climate change, ozone
depletion, toxic pollution of air, sea and land, and loss of biodiversity. Hence, it has been
widely accepted that the world cannot confront the severe environmental challenges it
faces without the necessary international cooperation. International environmental law
includes a large body of principles and rules that apply bilaterally, regionally and
internationally in order to address the environmental threats that are not restricted by
national boundaries. In 1996, the International Court of Justice (ICJ) took a significant step in
recognizing the existence of rules of general international environmental law, by stating that
states do in fact have an obligation to ensure that activities within their jurisdictional
boundaries are conducted in a manner that is respectful of surrounding states’
environments.
Despite customary rules largely playing a secondary role in international environmental law,
they can still develop legally binding obligations for states and have also influenced the
establishment of various environmental treaties and agreements. However, it is also
important to note that customary rules do not apply to states that can provide evidence of a
persistent objection to a practice as confirmed in the North Sea Continental Shelf case. As
such, customary international law requires 2 elements to be fulfilled in order for it to
satisfactorily be deemed customary international law, this includes evidence of a consistent
state practice and opinion juris. An established state practice can in fact contribute to the
development of customary law, as was confirmed by the ICJ in the Military and Paramilitary
Activities case, where it was held that customary rules can either be identical to treaty laws
or exist simultaneously along with the obligations of a treaty. In order for a practice to be
regarded as state practice it requires that it be a settled practice that is consistent and
uniform, that is generally followed by states, but it does not have to be strictly followed by
all states of the globe or in a region in order for it to constitute a state practice. While opinio
juris requires evidence that a state believes that they are bound by a certain custom or to
act in a certain based on its belief that it is required to do so by law. The ICJ in the North Sea
Continental Shelf case identified the content and role of opinion juris when they stated that
the act must not only be a state practice but also be carried out in a way that the state
believes they are obliged to abide. Although customary international law is based on the
required existence of these 2 elements, opinion juris is often more difficult to prove as it
requires one to determine the motives upon which acts conducted by a state were relied
upon.
Principles of IEL
The existence of the principles of international environmental law was confirmed in the Iron
Rhine case. There are various types of principles of international environmental law,
including sovereignty and responsibility, preventative action, cooperation, sustainable
development, precautionary principle, polluter pays principle and the common but
differentiated responsibility principle. These principles all represent a broad and general
approach in that they can be potentially applied to members within the international
community across a range of activities related to the environment, however it remains
difficult to determine their exact content and status. Each principle has a different legal
status, as some principles constitute rules of international environmental law, other
principles reflect emerging legal obligations, while the remaining principles represent a
much smaller legal status. Only the first 4 principles, sovereignty, preventative, cooperation
and precautionary could be regarded as rules of customary international law. Although it is
important to note here that precautionary principle would only be relevant in terms of the
European context, but it could also be deemed as a principle for certain global issues or
activities. The principle of sustainable development is regarded as an emerging principle,
while the last two principles being the polluter pays principle and the common but
differentiated principle are the least developed two which only appear in some treaties and
agreements and thus cannot be deemed as a rule of international environmental law, nor as
a cause of action against another state.
Sovereignty
The principle of sovereignty and responsibility is regarded as the cornerstone of
international environmental law (Sands and Peel). It essentially entails that states possess
permanent sovereignty over their natural resources, however they remain responsible to
ensure they do not engage in activities that will ultimately result in transboundary damage.
Important to note is that prior to the establishment of international environmental law,
state sovereignty was deemed absolute in the sense that states could freely utilize their
resources within their jurisdiction without any regard of the impact it might have on
neighbouring states. This unlimited notion of sovereignty soon shifted to one based on the
good of neighbourliness rooted and conserving the environment. Hence, the responsibility
of such a duty to not cause damage to the environment of other states is derived from the
duty to respect and recognize the territorial sovereignty of neighbouring states and the
impact one’s activities could have on that neighbouring territory. The representation of this
principle of sovereignty and responsibility was depicted in various judgements in various
early cases and disputes, such as in the Trail Smelter arbitration where the Arbitral Tribunal
held that “no state has the right to use or permit the use of its territory in such a manner as
to cause injury by fumes in or the territory of another” The Corfu Channel case, where the
ICJ held that a State has an “obligation not to allow knowingly its territory to be used for
acts contrary to the rights of other States”. As well as the Lac Lanoux arbitration where the
Tribunal emphasized that states must take into account the interests of a neighbouring state
when conducting activities that could impact the environment. Subsequent to these
judgements, the United Nations inferred these principles and formally adopted them in
Principle 21 of the Stockholm Declaration and Principle 2 of the Rio Declaration, which
reiterate that states have the sovereign right to exploit their own natural resources in line
with their own environmental policies. Principle 21 was so influential that the language of
the provision was not altered almost 2 decades later when they introduced Principle 2 in the
Rio Declaration. These principles essentially consist of 2 components, being the states
sovereign rights over natural resources as well as the no harm aspect. In terms of the
sovereign rights, a state has the right to control the exploitation over their own natural
resources within their jurisdiction, while the harm aspect entails that states are obliged to
ensure that they do not cause damage or harm to surrounding states environment or to
environments that are beyond the area of the limits of national jurisdiction. Finally, in the
Advisory Opinion on the Legality of the threat or Use of Nuclear Weapons, the ICJ confirmed
that principle 21 of the Stockholm Declaration reflected international law as it stated that,
“The existence of the general obligations of States to ensure that activities within their
jurisdiction and control respect the environment of other States or of areas beyond national
control is now part of the corpus of international law relating to the environment.” The ICJ’s
dissenting opinion also reiterated this notion as it stated that, “These principles of
environmental law thus do not depend for their validity on treaty provisions. They are part
of customary environmental law. They are part of the sine qua non for human survival.”.
Prevention
Furthermore, the responsibility of a state to not cause damage to the environment of
another states also reflects the principle of the duty of prevention, as it requires the state to
conduct activities with due diligence when exercising its sovereignty over natural resources.
The principle of preventative action essentially entails that states ought to prevent damage
and/or harm to the environment, and reduce, limit or control the activities that might result
in such harm. The principle requires that states act with due diligence to prevent such
damage to the environment, as well as a degree of vigilance in their enforcement and
exercise of administrative control and/or monitoring of activities. Important to note here is
that the principle of prevention does not guarantee that significant harm will be prevented,
however it does include an obligation imposed upon a state in order for it to ensure that all
steps and efforts are taken to minimise and/or reduce the risk or severity of harm occurring.
Thus, the principle does not impose an absolute obligation, but rather a relative obligation
on states. This principle of prevention also constitutes a rule of international customary law
as the notion of it exists in various legal instruments and mechanisms which concern the
prior assessment of environmental harm, licensing or authorization which entail the
conditions and consequences of violations of such conditions, as well as the adoption of
policies (Sands & Peel). It is evidently linked to principle 21 of the Stockholm Declaration
and Principle 2 of the Rio Declaration in respect of the no harm aspect. The existence of the
references of a duty to prevent and/or cause no harm as well as to take the necessary
measures to reduce such a risk of harm is evident in various instruments including but not
limited to provisions in the Ozone Convention, the MARPOL Convention, and article 194 of
UNCLOS which states that, “states … all measures … necessary to prevent, reduce and
control pollution for the marine environment from any source…”. The Corfu Channel case is
also significant for the principle of prevention as the UCJ did make reference to the fact that
states ought to notify another state in order to prevent any harm to occur to the other
state, hence the duty of notification also resonates with the principle of the duty to prevent
harm. The Pulp Mills case was probably the most significant case relating to this principle as
the ICJ held that, “‘The principle of prevention, as a customary rule, has its origins in the due
diligence that is required of a State in its territory. ... A State is thus obliged to use all the
means at its disposal in order to avoid activities which take place in its territory, or in any
area under its jurisdiction, causing significant damage to the environment of another State”.
Not only did the ICJ give credibility to the content of the principle of prevention, but it also
confirmed its legal status as a part of international customary law by stating that, “In this
sense, the obligation to protect and preserve, ... which in recent years has gained so much
acceptance among States, ...may now be considered a requirement under general
international law…”. Thus, it could be said that the principle of prevention encompasses
measures that are taken to prevent harm such as a duty of notification, a duty to undertake
environmental impact assessments, the duty of vigilance, as well as applications of the
principle through the limits on emissions and the standards on dangerous products. These
measures and principles could develop obligations on a state to protect the environment
from damage, and as a result it could be effectively used to rely on as a cause of action for
international liability in the violation of the principle of prevention of harm to the
environment.
Cooperation
The principle of cooperation is essentially an extension of the principle of good
neighbourliness that is linked to the principle of sovereignty. The principle imposes a
general duty on states to cooperate with one another in order to protect the environment.
This principle of cooperation is based on the shared values that states ought to practice as
environmental threats do not respect jurisdictional boundaries, as a result it highlights the
necessity of good faith, good neighbourliness, and non-discrimination against other states.
Cooperation is undoubtedly needed between states across the globe to confront the
emerging threats of environmental damage, particularly when it comes to shared border
lines. In this aspect, cooperation can include measures taken such as the exchange of
information, a duty of notification as well as consultation with another state. The principle
of cooperation is reflected through Principle 24 of the Stockholm Declaration, as well as
Principle 7 of the Rio Declaration. Principle 7 of the Rio Declaration can be divided into 2
aspects, firstly the duty to cooperate in a spirit of global partnership, as well as the common
but differentiated responsibilities. Principle 7 makes specific reference to states, however it
is important to note that the notion of global cooperation can be inferred upon non-state
actors too, such as international organisations and companies, as they often constitute
actors who are deemed contributors to pollution. The duty to cooperate is already a wellestablished principle in international instruments as it exists in articles 55 and 56 of the
Charter of the United Nations. The principle of cooperation was further reaffirmed in the
MOX Plant case, where ITLOS held that the duty to cooperate in the exchange of vital
information concerning the potential risks to the environment constitutes a fundamental
principle in the prevention of pollution in terms of UNCLOS and other international law.
Precautionary
The precautionary principle entails that when there are threats of serious and/or
irreversible damage or harm, then scientific uncertainty should not be relied upon as a basis
for measures to prevent environmental degradation. The core of the principle of
precautionary is reflected in Principle 15 of the Rio Declaration, which was in fact one of the
first codifications of the precautionary principle. Principle 15 states that, “In order to protect
the environment, the precautionary approach shall be widely applied by States according to
their capabilities. Where there are threats of serious or irreversible damage, lack of full
scientific certainty shall not be used as a reason for postponing cost-effective measures to
prevent environmental degradation”. The language utilised in principle 15 is more restrictive
than other instruments as it emphasises that the threats of damage must be serious or
irreversible. Additional formulations of the precautionary principle have subsequently
developed in the Preamble of the Convention on Biological Diversity (CBD), as well as article
3(3) of the Climate Change Convention (CCC). The Preamble of the CBD differs in that it
makes reference to “a threat of significant reduction or loss of biological diversity”, hence it
more flexible than the more serious and/or restriction notion of Principle 15. In terms of
article 3(3) of the CCC, part of it is the exact formulation of principle 15, however the other
aspect of it takes a more action-orientated approach in that it requires states to take
precautionary measures to prevent the cause of climate change, and/or to reduce its
effects. The principle of the precautionary principle has also reflected in various
international disputes, it first appeared in the ICJ in a case concerning French nuclear
testing, instituted by New Zealand, where it reinforced the notion that this principle is a rule
of international customary law. However, the ICJ did not rule on that aspect, but it did
affirm that the precautionary principle was in fact gaining increasing support of the
international community in relation to the environment. In the Gabcikovo-Nagymaros case,
the ICJ also elected not to address the status of the precautionary principle, however
Hungary did rely its argument on the fact that the parties had agreed to precautionary
measures in regards to the environment. In the Pulp Mills case, the ICJ had shifted its
position and addressed the precautionary principle to an extent. Despite not formally
confirming its legal status as a rule of international customary law, the ICJ still affirmed that
the precautionary principle did in fact have some status, and was not a principle without any
effect. In the Southern Bluefin Tuna cases, in response to a request to require the parties to
act consistently with the precautionary principle, ITLOS held that the parties ought to “act
with prudence and caution to ensure that effective conservation measures are taken to
prevent serious harm to the stock of southern bluefin tuna”. ITLOS judgement was also one
deemed to be a precautionary approach as the parties were imposed upon a limitation upon
which to comply with when conduct fishing related activities in order to avoid depleting the
stock of the fish. This imposing of a limitation represented ITLOS enforcing a measure
sourced from the precautionary principle. Despite there being uncertainty in terms of its
legal status globally, it has been largely embraced as a rule of international customary law in
the European region based on the fact that it arose in West Germany and grew to popularity
in Europe in the 1980s before being codified in the Rio Declaration. The principle has not
only informed many EU policies, but it has also further reaffirmed in the European context
by its codification in article 191 of the Treaty of Lisbon as well as a Communication issued by
the European Commission. All of these acknowledgements of the precautionary principle in
both European regional law and case decisions has reflected its stance that it is an rule of
international customary law within the context of Europe, and as such its continued
application and influence on international instruments and case decisions should impose
upon it the equal legal status it shares in Europe.
Despite the applicability of international environmental principles being widely
acknowledged and utilized by the international community, their legal status as
international customary law rules is still often debated and contentious. This formal lack of
certainty in the legal status of these principles of international environmental law is largely
due to the fact that these principles emerged over a short period of time within the last 2 or
3 decades which often create a presumption to opponents that they cannot constitute
custom due to their “short-term” existence. Opponents to the recognition of principles of
international customary law also rely on the fact that the meaning of the principles often
exist in contrast to what they mean in practice, as is evident in the precautionary principle,
as well as the ever evolving interpretation and extent of application of these principles on
both an international and regional scale. There will always exist states that do not wish to
recognize the principles of international environmental law as binding rules of international
customary law as it would require them to oblige to liability for violations of such principles
that aim to conserve the environment. However, despite these arguments against the
recognition of these principles as international customary law, most states and international
courts and tribunals have relied on these principles and rules to justify their actions in
regard to environmental related matters. These principles are often relied on by presiding
officers when making judgement in order to result in a decision that also aids in protecting
the environment.