A more recent version of these Sources notes – written by Oxford students – is available here.
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A. THE CONCEPT OF INTERNATIONAL LAW 'International law' refers to the body of rules and principles that regulate States in their relations with each other. But States are not the only subjects of international law: international organisations and, to a lesser extent, individuals can also bear rights and duties under international law. The key organising principles of international law are Sovereignty, Territory, Nonintervention, Equality, Consent and Responsibility.
B. WHY IS INTERNATIONAL LAW BINDING?
Two main theories explain the binding force of international law: natural law and positivism. International law is a positivist system of law, in that to be binding rules must have been adopted through one of the recognized means of law creation (treaty, custom or general principles of law). The ICJ held in South West Africa (Ethiopia v South Africa) that humanitarian considerations are not sufficient in themselves to generate legal rights and obligations. The Court can take account of moral principles only insofar as these are expressed in legal form. In international law, positivism has taken the form of voluntarism: it is the (common) will of States which gives international law its authority as law. The sources of international law (treaties, customary law, and general principles) all derive their binding source from State consent, which can be given expressly or implicitly (Lotus(France v Turkey)). However, voluntarism cannot explain why new States become bound by general international law even if they have not consented to it; and, second, it cannot explain why States may not withdraw, as a matter of general international law, from customary rules. D'Amato (1984) argues that international law is enforced through a system of reciprocal entitlements, such as the entitlement of statehood. Statehood means that the nation is a geographic entity entitled to exert its own legal jurisdiction in the area within its boundaries and to claim the inviolability of those boundaries against all other states. Yet the borders remain as such only by virtue of their recognition by other states, such that this entitlement may be said to carry with it reciprocal duties. The entitlement provides that the nation must respect the borders of other states, otherwise tit-for-tat transgression of each other's borders would endanger the existence of the states in question. A nation is nothing more nor less than a bundle of entitlements, such as the entitlement to enter into binding treaties with other nations, to a territorial sea etc.
Further, many of the idea and principles of international law today are rooted in the notion of Natural Law and the relevance of ethical standards to the legal order, such as the principles of non-aggression and human rights.
C. SOURCES OF INTERNATIONAL LAW Lack of a legislature, executive and structure of courts within international law. One is therefore faced with the problem of discovering where the law is to be found and how one can tell whether a particular proposition amounts to a legal rule. Nevertheless, there are 'sources' from which the rules of international law may be extracted. A distinction is often drawn between 'formal' and 'material' sources. Formal sources are the processes through which rules of international law are created (e.g. the passage of a Bill through Parliament is a formal source of law) eg Art 38(1)(a),(b),(c)......IT IS LAW. Material sources refer to the actual document or place in which the rule is included (eg, a treaty or a United Nations resolution) eg Art 38(1)(d)......PROVIDES EVIDENCE OF LAW. Standard point of departure: Art 38 of the Statute of the International Court of Justice (ICJ)
1. The Court, whose function is to decide in accordance with international law such disputes as are submitted to it, shall apply: a. international conventions, whether general or particular, establishing rules expressly recognized by the contesting states; b. international custom, as evidence of a general practice accepted as law; c. the general principles of law recognized by civilized nations; d. subject to the provisions of Article 59, judicial decisions and the teachings of the most highly qualified publicists of the various nations, as subsidiary means for the determination of rules of law.
2. This provision shall not prejudice the power of the Court to decide a case ex aequo et bono, if the parties agree thereto. Is this an exhaustive statement of the sources of international law? It is arguable that Art 38 is only a direction to the court authorising it to consider various materials when deciding disputes submitted to it. It does not provide a complete list of the matters which the Court in fact considers. Art 38 makes no reference to resolutions of the UN General Assembly or to diplomatic correspondence, both of which figure prominently in the court's judgments. Purpose of customary law -> as the DEFAULT POSITION when there are no treaties available
1. TREATIES Baxter paradox -> where there is a widely ratified treaty, harder to get evidence of opinio juris for state conduct because the practice follows the obligations during the treaty and not because those states think that practice should be a customary law
2. CUSTOM (i) General customary Law There are two requirements of custom: a (i) 'general practice' (state practice), which must be (ii) 'accepted as law' (opinio juris) (North Sea Continental Shelf (Germany v Denmark)). The relative importance of the two factors is disputed by various writers. Positivists such as Anzilotti (1928) stress the paramount importance of the psychological element. States are only bound by what they have consented to, so therefore the material element is minimised to the greater value of opinio juris. If states believe that a course of action is legal and perform it, even if only once, then it is to be inferred that they have tacitly consented to the rule involved. Following on from this analysis, various positivist thinkers have tended to minimise many of the requirements of the overt manifestation, e.g. with regard to repetition and duration. Evidence of customary law must not be searched only in the conduct of the States actively engaging in the practice. It must also take into account the reactions of other States: whether they accept the conduct or protest it. Customary law is formed in the dynamic of claim and response between States. (a) The material element of customary law: State practice State practice consists of any act or statement by a State (any organ of the State) which can evidence its views about customary law. Such acts include the judgements of national courts, legislation, claims advanced by States before foreign courts and statements made by state representatives. To generate a rule of customary law, the practice must be general, consistent, and of a certain duration. (1) Generality While not all States must engage in the practice, there must be sufficient examples on the part of a sufficient number of States. In North Sea Continental Shelf (Germany v Denmark), the ICJ held that the degree of generality will vary with the subject matter, so that an onerous customary law obligation may require a more general practice than a norm which gives a state limited privileges. In assessing whether a customary rule has come into existence, special weight may be given to the practice of those states whose interests are specifically affected by the subject matter of the rule. For example, the
practice of major maritime powers will have more significance in the formation of rules on the law of the sea than landlocked states. (2) Consistency and uniformity Overall consistency, such that instances of State conduct inconsistent with the rule should have been treated as breaches of that rule and not as indications of the recognition of a new rule, would be sufficient. The degree of consistency required may vary according to the subject matter of the rule in dispute. Asylum Case (Columbia v Peru) (Peru rebel granted asylum by Columbia in Peruvian Embassy. Columbia brought the case against Peru to compel Peru to grant safe passage out of Peru. Columbia argued there was a rule of unilateral and definitive qualification for asylum was a customary rule and invoked a large number of cases where diplomatic asylum was granted and respected)?ICJ held there was no such customary law to grant asylum as:
1. Much fluctuation and discrepancy in the (a) exercise of diplomatic asylum and (b) official views expressed on varied occasions
2. Much inconsistency in the rapid succession of conventions on asylum, ratified by some states and rejected by others
3. Practice has been influenced by much political expediency
-> Therefore it was not possible to discern any CONSISTENT or UNIFORM usage ICJ further held that even if such a custom could be established specific to only the Latin-American States, such a custom could not be invoked against Peru as Peru has repudiated such a custom by refraining from ratifying the Montevideo Convention of 1933 and 1939 (which was first to include a rule concerning the qualification of the offence in matters of diplomatic asylum)
-> Shows that consistent refusal to acknowledge a position (especially since Peru has been opposing such diplomatic asylum from the onset - as Montevideo was the FIRST) can be taken to mean that even a custom (if it exists in the first place) cannot be applied to it Thus, if we are dealing with POSITIVE OBLIGATIONS, as where a state is obliged to protect foreign nationals in its territory, a GREATER DEGREE OF CONSISTENCY may be needed for the formation of a customary norm than in the case where a state is obliged to refrain from doing something.
(3) Duration A short period of time is sufficient so long as there is evidence of widespread participation by States This raises the possibility that even a single act, without subsequent repetition, can be the basis for custom. Although such 'instant' custom is a possibility, it would require very strong evidence that states regarded the new practice as legally binding. A relevant factor is the strength of the prior rule which is purportedly overthrown. Bin Cheng (1997) notes that the principle of nonsovereignty over the space route followed by artificial satellites came into being
soon after the launching of the first sputniks. Thus, 'instant' customary law is more likely where there is no prior rule. (4) The role of silence Evidence of customary law may also be found in silences and abstentions. In Lotus (France v Turkey) (French and Turkish steamer collided in the HIGH SEAS, Turkey wanted to proceed with criminal proceedings against the French sailors. French argued that a custom could be seen that States do not institute criminal proceedings against members of other sovereign states for incidents occurring in the HIGH SEAS but instead leave it to those sovereign states and thus the criminal charges should be dropped),-
PCIJ dismissed the French government's argument that because of the rarity of States instituting criminal proceedings (in this case Turkey against French sailors during Turkish law), they have "not recognised themselves as being obliged to do so" The PCIJ declared that abstention could only give rise to the recognition of a custom if it was based on a conscious duty to abstain.
? Thus, one cannot infer a rule prohibiting certain action merely because states do not engage in that activity.
? In this case no evidence that abstention was motivated by any "legal obligation"
Even if it does not create custom, inaction may communicate the acquiescence of States. ICJ in Gulf of Maine (Canada v USA) defined acquiescence as tacit recognition which the other party may interpret as consent, founded upon the principles of good faith. It must be based upon full knowledge of the rule invoked, and may have the effect of legitimising the behaviour. (5) Evaluation The duration and generality of a practice may take second place to the relative importance of the states precipitating the formation of a new customary rule. For a custom to be accepted and recognised, it must have the concurrence of the major powers in that particular field. A regulation regarding the breadth of the territorial sea is unlikely to be treated as law if the great maritime nations do not agree to or acquiesce in it, no matter how many landlocked states demand it. (b) The subjective element of customary law: Opinio juris sive necessitates Opinio juris means that the practice must be adopted in the belief that it was rendered obligatory or permissible by a rule of customary international law (North Sea Continental Shelf) Opinio juris encompasses both:
1. Static aspect (the belief that a practice is a rule of customary law, that it is 'accepted as law')
2. Dynamic one (the belief that a practice should be a rule of customary law) In North Sea Continental Shelf, the ICJ said that 'the frequency or even habitual character' of a practice is not enough to establish opinio juris. The degree of proof required for opinio juris will vary according to the subject matter of the disputed customary rule. A claim that a rule has attained the status of jus cogens would require very clear evidence of opinio juris. (1) Conceptual difficulties The opinio juris concept is tautologous for it suggests that something must be considered as obligatory because of an existing rule of customary international law before it can become customary international law. (2) Practical difficulties It may sometimes be hard to pinpoint the existence of opinio juris. One approach is to infer or deduce the opinio juris from material acts. Judge Tanaka (dissent) in North Sea Continental Shelf, argued that we have to ascertain the existence of opinio juris from the external existence of a certain custom, rather than seek evidence as to the subjective motives for each example of State practice.' The current systems suggests that the judges just ASSERTS that there is customary law (Judge Tanaka did not use the word assert)
-Judge Tanaka's dissent hints at rule-scepticism, that opinio juris seems to be what the courts make it out to be, cloaked in legal language. That opinio juris can be used by the ICJ to say there is no custom when there is widespread practice and vice versa, allowing the ICJ to effectively unilaterally decide if there is custom or not
? Criticism -> Can't rule out what Judge Tanaka says about rule scepticism, but the current structure provides at least a FRAMEWORK in which law is created. Though the concept of how much state practice is required and whether opinio juris is present is an ELASTIC CONCEPT, litigant states would still refer to them in framing their arguments in front of the court. In conclusion, one cannot shut down speculation about rule scepticism, but the existing framework at least allows for an alternative plausible explanation of the law
In Jurisdictional Immunities (Germany v Italy), the ICJ found the opinio juris in the very consistent practice of domestic courts and the repeated and unvarying public statements of governments. It held that state practice and opinio juris evidenced that customary international law continues to require that a State be accorded immunity in proceedings for torts allegedly committed on the territory of another State by its armed forces and other organs of State in the course of an armed conflict.
Faced with the difficulty in practice of proving the existence of the opinio juris, increasing reference has been made to conduct within international organisations. For example, in Nuclear Weapons, the ICJ used General Assembly resolutions to determine whether there was opinio juris for a customary law rule
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