• Dan Canta

Article 38(1)(b) Crystallization


Under Article 38(1) of its Statute, the International Court of Justice (the ‘Court’) may only apply law that is considered a general principle or contained in international conventions, judicial decisions, teachings of the most highly qualified publicists and that which is considered international custom.[i]

This paper aims to discuss how customary international law (‘CIL’) is formed (A),[ii] how a treaty may reflect CIL (B), and how a State can avoid compliance (C).

A. Formation

Under Article 38(1)(b) of the ICJ Statute, international custom is evidenced by general practice accepted as law.[iii] Consequently, the formation of CIL requires satisfaction of two elements, the first objective and the second, psychological:

1. State practice; and,

2. Opinio Juris.[iv]

While resolutions adopted by international organisations or intergovernmental conferences cannot, of itself, create a rule of CIL, adoption may provide evidence toward the existence and/or contribute to the development of said rule.[v] Further, decisions of the Court and the teachings of the most highly qualified publicists concerning the existence of rules of CIL are merely a subsidiary means of their formation.[vi]

1. State Practice

The objective element of CIL requires the acceptance of law to be evidenced by uniform usage and widespread adoption by States.[vii] Such practice consists of conduct of the State in exercise of its legislative, judicial, executive, or other functions.[viii]

State practice may include physical and verbal actions, and in some instances, inaction.[ix] However, practice does not necessitate an expression of consent by a certain State to be bound, rather widespread international acceptance and usage.[x] There is no specific length of time the practice is required to have existed.[xi]

Despite requiring extensive usage, the law need not be universal among States.[xii] In following this, the Court has ruled ‘long continued practice between two States…regulating their relations.... [and forming] the basis of mutual rights and obligations’ may create CIL between them.[xiii]

2. Opinio Juris

The psychological element of CIL requires practice to derive from a State’s view that such practice is obligated by law.[xiv] In S.S. Lotus, the Court held that uniform practice in abstaining from instituting criminal proceedings could not form CIL, where recognition of a duty to do so was required.[xv] In the North Sea Continental case, the Court upheld this treatment by rejecting general CIL in respect to boundary lines, as the specific rules were those which created obligations for States.[xvi]

Forms of evidence of acceptance of a legal obligation States include:

“public statements made on behalf of States; official publications; government legal opinions; diplomatic correspondence; decisions of national courts; treaty provisions; and conduct in connection with resolutions adopted by an international organization or at an intergovernmental conference.”[xvii]

B. Treaty Reflection

A treaty provision may reflect a rule of CIL if it codifies an existing rule of CIL, resulted in the crystallization of an emerging CIL rule, or gave rise to a general practice that is now accepted as law.[xviii]

C. Avoiding Compliance

While CIL is generally inviolable, States may abrogate if they are a persistent objector to the rule or in instances of conflicting treaty obligations.[xix] These exceptions do not apply to jus cogens norms.[xx]

1. Persistent Objector Rule

A State may derogate from its obligations under CIL if it has always opposed the rule and any attempts to apply it.[xxi] Opposition must be clearly expressed to other States, raised during its formative stages, and maintained consistently.[xxii]

The Inter-American Commission on Human Rights (‘IACHR’) rejected the persistent objector defence for jus cogens norm violations by the United States, however expressly recognised its legitimacy otherwise.[xxiii]

2. Conflicting Treaty Obligations

While Article 38 of the ICJ Statute does not provide a strict hierarchy of the sources of law, the Court has held lex specialis (specific rule prevails over general rule) treaty obligations could not operate to deprive States of their rights under CIL.[xxiv]

Where two CIL principles conflict with one another, the more specific rule prevails. For example, the Court adopted a presumption of continuance of territorial regimes following succession over the clean slate doctrine, despite both being CIL principles.[xxv]

Further, lex superior (laws of a superior hierarchy prevail over others) operates to exclude abrogation of jus cogens norms, where conflicting treaty obligations may result in an abrogation of a rule of CIL if the other is a jus cogens norm.[xxvi]

3. Jus Cogens Norms

A Jus Cogens norm is a rule that the international community as a whole accepts cannot be derogated from, under any circumstances.[xxvii] For instance, prohibitions against torture and the acquisition of territory through war have acquired the status of jus cogens.[xxviii]

Any legal obligation or treaty that conflicts with a jus cogens norm, including those of CIL status, is rendered void.[xxix] The IACHR, for instance, rejected the use of a treaty dating back to 1762 as a defence as said treaty ‘would today be null and void because it contradicts the norms of jus cogens superveniens.’[xxx]

Dan Canta

Chief Publications Officer & Director - Article 33 Institute


[i] Statute of the International Court of Justice art 38(1) (‘ICJ Statute’). [ii] ICJ Statute (n i) art 38(1)(b). [iii] ICJ Statute (n i) art 38(1)(b). [iv] Right of Passage over Indian Territory (Portugal v India) (Merits) [1960] ICJ Rep 6, 37 (‘Right of Passage’); International Law Commission, Draft conclusions on identification of customary international law, 70th session, 3412th mtg (25 May 2018) 2 (‘ID CIL’). [v] ID CIL (n iv) 4. [vi] ID CIL (n iv) 4. [vii] Asylum (Columbia v Peru) (Judgment) [1950] ICJ Rep 266, 276; ID CIL (n) 2. [viii] ID CIL (n iv) 2. [ix] ID CIL (n iv) 2. [x] North Sea Continental Shelf Cases (Federal Republic of Germany/Denmark v Federal Republic of Germany/Netherlands) (Judgement) [1969] ICJ Rep 3, 38-9 (‘North Sea’). [xi] Fisheries Case (United Kingdom v Norway) (Judgement) [1951] ICJ Rep 116, 74 (‘Fisheries Case’). [xii] North Sea (n x) 74. [xiii] Right of Passage (n iv) 37; See also ID CIL (n) 4. [xiv] Right of Passage (n iv) 37, 44. [xv] S.S. Lotus (France v Turkey) (Judgement) [1927] PCIJ (ser A) No 10 [76]. [xvi] North Sea (n x) [78]. [xvii] ID CIL (n iv) 2. [xviii] ID CIL (n iv) 3. [xix] Case Concerning Armed Activities on the Territory of the Congo (Democratic Republic of the Congo v Uganda) (Judgement) [2005] ICJ Rep 168, [337]; Fisheries Case (n) 131. [xx] ID CIL (n iv) 4. [xxi] Fisheries Case (n xi) 131. [xxii] ID CIL (n iv) 4. [xxiii] Domingues v United States (Inter-American Commission of Human Rights, Merits Case 12.285, 22 October 2002) [48] (‘Domingues’). [xxiv] Legality of the Threat or Use of Nuclear Weapons (Advisory Opinion) [1996] ICJ Rep 226 [30]. [xxv] Gabčíkovo-Nagymaros Project (Hungary v Slovakia) (Judgment) [1997] ICJ Rep 7 72-3; Temple of Preah Vihear (Cambodia v Thailand) (Judgment) [1962] ICJ Rep 6 34, 40; Right of Passage (n) 40; Free Zones of Upper Savoy and the District of Gex (France v Switzerland) (Judgment) [1929] PCIJ (Ser A) No 22; See International Law Commission (ILC), Draft articles on Succession of States in respect of Treaties with commentaries, 26th sess, 1301st mtg (26 July 1974) 197-9, 198, 205, 212, 216, 238-40, 261. [xxvi] Domingues (n xxiii) [85]. [xxvii] Vienna Convention on the Law of Treaties, opened for signature 23 May 1969, 1155 UNTS 331 (entered into force 27 January 1980) art 53, 64. [xxviii] Prosecutor v Furundzija (Judgement) (International Tribunal for the Prosecution of Persons Responsible for Serious Violations of International Humanitarian Law Committed in the Territory of the Former Yugoslavia since 1991, Trial Chamber, IT-95-17/1-T, 10 December 1998) [144], [153]. [xxix] Vienna Convention on the Law of Treaties, opened for signature 23 May 1969, 1155 UNTS 331 (entered into force 27 January 1980) art 53, 64. [xxx] Aloeboetoe et al. Case (Inter-American Commission of Human Rights, 10 September 1993) [56]-[57].

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