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Can Quantitative Methods Complement Doctrinal Legal Studies? Using Citation Network and Corpus Linguistic Analysis to Understand International Courts


A recent editorial in this journal stressed the need to rearticulate the methodology – and thereby the distinctiveness – of international law in the context of blurring disciplinary lines between international law and international relations. The aim of this article is to contribute to the methodological aspect of the debate. First, the article outlines a legal empirical approach, which complements legal methodology of international law with empirical tools and techniques such as citation network analysis and corpus linguistics. Second, the article applies the approach on the case law of two European courts: the Court of Justice of the European Union (CJEU), and the European Court of Human Rights (ECtHR). It demonstrates how the study of case citations and the language of courts enhance the validity, reliability, and transparency of the established legal method. In particular, scholars of international law gain a stable and complete quantitative basis for a further in-depth study of case law, precedent and interpretation. Additional benefit stems from a set of transparent criteria by which to criticize the jurisprudence of international courts. Firmer ground emerges from which to evaluate the courts’ role in the political process, their societal impact and their legitimacy. At the same time the approach preserves the main features of the distinct legal methodology of international law – especially its attention to legal detail.

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1 Venzke, I., ‘International Law and Its Methodology: Introducing a New Leiden Journal of International Law Series’, (2015) 28 Leiden Journal of International Law 185 , at 187.

2 Klabbers, J., ‘Whatever Happened to Gramsci? Some Reflections on New Legal Realism’, (2015) 28 Leiden Journal of International Law 469 . Koskenniemi, M., ‘Law, Teleology and International Relations: An Essay in Counterdisciplinarity’, (2012) 26 International Relations 3 .

3 Determining whether these courts are international courts is not straightforward. While the ECtHR is regularly considered an international court, the CJEU is often perceived as something separate or sui generis, especially due to the alleged distinctiveness of the European legal order. In texts that address the global international legal order, the CJEU is, however, treated as an international court. See K.J. Alter, The New Terrain of International Law: Courts, Politics, Rights (2014). Similarly, manuals on international adjudication include the CJEU among international courts, and fit it into the category of courts of regional economic and/or political integration agreements. See Romano, C., Alter, K.J., and Shany, Y. (eds.), The Oxford Handbook of International Adjudication (2014).

4 The website of the East African Court of Justice, available at (accessed 25 October 2016).

5 See for instance Tarissan, F. and Nollez-Goldbach, R., ‘Analysing the First Case of the International Criminal Court from a Network-Science Perspective’, (2016) 4 Journal of Complex Networks 616 .

6 Ibid.

7 Ibid., in particular the relative in degree. We discuss further limitations and propose solutions in Section 3.

8 On this matter see Vauchez, A., ‘Methodological Europeanism at the Cradle: Eur-Lex, the Acquis and the Making of Europe's Cognitive Equipment’, (2015) 37 Journal of European Integration 193 . New technology is also increasingly changing access to statutory legislation, and with new translation engines there is also a growing awareness of foreign law across domestic jurisdictions. In this article, however, we only focus on the application of computational technology to the case law of the CJEU and the ECtHR.

9 Katz, D.M., ‘Quantitative Legal Prediction – or – How I Learned to Stop Worrying and Start Preparing for the Data Driven Future of the Legal Services Industry ’, (2013) 62 Emory Law Journal 909 .

10 See generally K. Zweigert and H. Kötz, Introduction to Comparative Law (1998). For the role of legal scholarship in Germany, and the German influence in systematizing European Union law, see Vogenauer, S., ‘An Empire of Light? II: Learning and Lawmaking in Germany Today’, (2006) 26 Oxford Journal of Legal Studies 627 , at 657.

11 The overall theoretical framework for this approach is set out in normative legal theory. Dworkin refers to the seamless web of fit and justification, and his idea of law as integrity is based on coherence. R. Dworkin, Law's Empire (1986), xiii, 470. European legal theory also emphasizes coherence as a predominant criterion for legal validity, Alexy, R., ‘Coherence and Argumentation or the Genuine Twin Criterialess Super Criterion’, in Aarnio, A. et al. (eds.), On Coherence Theory of Law (1998), 41.

12 R.C.A. White and C. Ovey, Jacobs, White & Ovey: The European Convention on Human Rights (5th edn., 2010).

13 S. Müller-Mall, Legal Spaces: Towards a Topological Thinking of Law (2013).

14 This is less true for the studies of the CJEU. See Lindholm, J. and Derlén, M., ‘The Court of Justice and the Ankara Agreement: Exploring the Empirical Approach’, (2012) 3 Europarättslig tidskrift 462 .

15 Fowler, J.H. and Jeon, S., ‘The Authority of Supreme Court Precedent’, (2008) 30 Social Networks 16 . The idea is that a court disrespectful of precedent (an activist court) will cite fewer precedents than a court which is less activist (such a court will embed its decision in previous case law).

16 Black, R.C. and Spriggs, J.F., ‘The Citation and Depreciation of U.S. Supreme Court Precedent’, (2013) 10 Journal of Empirical Legal Studies 325 .

17 Lupu, Y. and Fowler, J.H., ‘Strategic Citations to Precedent on the U.S. Supreme Court’, (2013) 42 Journal of Legal Studies 151 .

18 Lupu, Y. and Voeten, E., ‘Precedent in International Courts: A Network Analysis of Case Citations by the European Court of Human Rights’, (2012) 42 British Journal of Political Science 413 . For a study of strategic litigation and the creation of precedents in the WTO see Pelc, K.J., 'The Politics of Precedent in International Law: A Social Network Application, (2014) 108 American Political Science Review 547 .

19 Lupu and Voeten, supra note 18, at 438.

20 Fowler, J.H. et al., 'Network Analysis and the Law: Measuring the Legal Importance of Supreme Court Precedents', (2007) 15 Political Analysis 324 , at 344.

21 For hubs and authorities see Kleinberg, J.M., ‘Authoritative Sources in a Hyperlinked Environment’, (1999) 46 Journal of the ACM (JACM) 604 . For page-rank see S. Brin and L. Page, ‘The Anatomy of a Large-Scale Hypertextual Web Search Engine’, available at (accessed 30 October 2016).

22 Kleinberg, supra note 21, at 604.

23 Civil law style courts are often said to cite fewer cases than common law style courts. The citation network of a common law style court will have more links between a given number of cases than the citation network of a civil law style court. The latter will thus be sparser. However, in both networks it will be equally possible to distinguish the central from the peripheral cases, and analyze the network structure.

24 The origin of this line of thought is Hart's discussion of Bentham's work on the method of elucidation of legal concepts, inspired by the philosophy of language. According to Bentham, in elucidating the meaning of legal words like right or duty or state, one should take into account not, ‘these words alone, but consider whole sentences in which they play their characteristic role’. H.L.A. Hart, Essays in Jurisprudence and Philosophy (1983), 26.

25 G. Letsas, A Theory of Interpretation of the European Convention on Human Rights (2009), 145. Letsas, G., ‘The Truth in Autonomous Concepts: How to Interpret the ECHR’, (2004) 2 European Journal of International Law 279 .

26 For a study of formulas in the case law of the Court of Justice of the European Union see Azoulai, L., ‘The “Retained Powers” Formula in the Case Law of the European Court of Justice: Eu Law as Total Law?’, (2011) 4 European Journal of Legal Studies 192 ; Azoulai, L., ‘La Fabrication De La Jurisprudence Communautaire’, in Mbongo, P. and Vauchez, A. (eds.), Dans La Fabrique Du Droit Européen: Scènes, Acteurs Et Publics De La Cour De Justice Des Communautés Européennes (Collection Droit De L'union Européenne. Colloques) (2009), 153–69; Šadl, U., ‘Case – Case-Law – Law: How the Court of Justice of the European Union Constructs Its Legal Arguments’, (2013) 9 European Constitutional Law Review 205 .

27 Cross, F.B., ‘The Ideology of Supreme Court Opinions and Citations’, (2012) 97 Iowa Law Review 693 .

28 Phraseology is a term that describes the tendency of words, and groups of words, to occur more frequently in some environments than others. S. Hunston, Corpus Approaches to Evaluation: Phraseology and Evaluative Language (2011), 5.

29 Sinclair's work is viewed as the origin of modern corpus linguistics. J. Sinclair, Corpus, Concordance, Collocation (1991).

30 Gozdz-Roszkowski, S. and Pontrandolfo, G., ‘Legal Phraseology Today: Corpus-Based Applications across Legal Languages and Genres’, (2015) 3–4 Fachsprache, International Journal of Specialized Communication 130 .

31 Hall, M.A. and Wright, R.E., ‘Systematic Content Analysis of Judicial Opinions’, (2008) 96 Cal. L. Rev. 63 .

32 This is a much simplified presentation of collocation. For more detail see C.D. Manning and H. Schütze, Foundations of Statistical Natural Language Processing (1999), 141 et seq.

33 See for instance Panagis, Y. and Šadl, U., ‘The Force of EU Case Law: An Empirical Study of Precedential Constraint’, (2015) 279 Legal Knowledge and Information Systems: JURIX 2015: The Twenty-Eighth Annual Conference 71 .

34 Effet utile is often associated with the ‘liberal interpretation’ of the Treaty. T. Tridimas, The General Principles of EU Law (2006), cxxi, 419. The same holds for German speaking scholarship. (See the literature cited in A. Von Oettingen, Effet Utile Und Individuelle Rechte Im Recht Der Europäischen Union (2010). See also Potacs, M., ‘Effet Utile Als Auslegungsgrundsatz’, (2009) 4 EuR 465 .) Recent literature broadens the legal context of effet utile considerably, discussing it against other principles of European law such as loyalty. See for instance, M. Klamert, The Principle of Loyalty in Eu Law (2014), or in the context of justification and argumentation, see M. Lasser, Judicial Deliberations: A Comparative Analysis of Judicial Transparency and Legitimacy (2009), 382. See also Marc A. Jacob, Precedents and Case-Based Reasoning in the European Court of Justice: Unfinished Business (2014), 25. Nevertheless, scholarship continues to treat it as an interpretive instrument (Klamert, ibid., at 255) either in the form of an emerging constitutional principle ( Ross, M., ‘Effectiveness in the European Legal Order(s): Beyond Supremacy to Constitutional Proportionality? ’, (2006) 31 E.L. Rev. 476 ), a meta rule of interpretation ( Mayr, S., ‘Putting a Leash on the Court of Justice? Preconceptions in National Methodology v Effet Utile as a Meta-Rule’, (2012/13) 5 European Journal of Legal Studies 8 ), or a meta-policy of the Advocates General and the CJEU (Lasser, ibid., at 212, 358.)

35 Dougan, M., ‘The Vicissitudes of Life at the Coalface: Remedies and Procedures for Enforcing Union Law before the National Courts’, in Craig, P. and De Búrca, G. (eds.), Evolution of EU Law (2011), 407 .

36 (accessed 27 October 2016).

37 The approach on the tagging and the extraction of paragraphs is described in detail in ‘omitted for peer review’.

38 Case 213/89, The Queen v. Secretary of State for Transport, ex parte Factortame [1990] ECR I-02433.

39 Case 106/77, Amministrazione delle finanze dello Stato v. Simmenthal [1978] ECR 00629.

40 Case 6/90, Francovich and Bonifaci v. Italy [1991] ECR I-05357.

41 Case 46/93, Brasserie du pêcheur v. Bundesrepublik Deutschland and The Queen / Secretary of State for Transport, ex parte Factortame and Others [1996] ECR I-01029.

42 Case 33/76, Rewe v. Bundesmonopolverwaltung für Branntwein [1976] ECR 01989; Case 45/76, Comet BV v. Produktschap voor Siergewassen [1976] ECR 02043.

43 Case 261/95, Rosalba Palmisani v. Istituto nazionale della previdenza sociale (INPS) [1997] ECR I-04025.

44 Case 199/82, Amministrazione delle Finanze dello Stato v. SpA San Giorgio [1983] ECR 03595.

45 Case 222/84, Johnston v. Chief Constable of the Royal Ulster Constabulary [1986] ECR 01651, C-222/86.

46 Case 222/86, Union nationale des entraîneurs et cadres techniques professionnels du football (Unectef) v. Georges Heylens and others [1987] ECR 04097.

47 Case 312/93, Peterbroeck, Van Campenhout & Cie v. Belgian State [1995] ECR I-04599.

48 Case 106/89, Marleasing v. Comercial Internacional de Alimentación [1990] ECR I-04135003.

49 Case 14/83, Von Colson and Kamann v. Land Nordrhein-Westfalen [1984] ECR 01891.

50 Case 379/98, PreussenElektra AG v. Schhleswag AG [2001] ECR I-02099.

51 Case 415/93, Union royale belge des sociétés de football association and Others v. Bosman and Others [1995] ECR I-04921.

52 Case 101/05, Skatteverket v. A. [2007] ECR I-11531.

53 Case 307/97, Compagnie de Saint-Gobain, Zweigniederlassung Deutschland v. Finanzamt Aachen-Innenstadt [1999] ECR I-06161.

54 In Figure 1 the network is composed of all paragraphs of all cases that contain the word ‘effectiveness’ in the network of all CJEU cases. The bigger the dots, the more central the case. Figure 1 visualizes only the labels (names of cases) and paragraphs of cases which are cited most often (more than seven times) in the network. This greatly improves the readability of Figure 1. When nodes are the same colour, this indicates that they belong to the same group of cases (clusters) based on their citation pattern. The latter means that they are more closely connected (cited) to the nodes of the same colour than to the nodes of another colour.

55 In a collocate cloud the same concept can be repeated in slight variations, for instance order to ensure (on the bottom right side) and of ensuring the (bottom left side).

56 Table 1 is an extract of all collocates. We omitted most collocates due to the difficulties with the visualization (for instance, in the 2000s we have more than 2,400 collocates). We listed the most frequent collocates and the most conspicuous collocates, which were relevant for our examples. The whole table and the reproduction files are on file with the authors.

57 The so-called t-score is a statistical measure of confidence with which we can assert that there is an association between words /concepts. t-score will yield significant collocates that occur relatively frequently.

58 Case 120/78, Rewe v. Bundesmonopolverwaltung für Branntwein (Cassis de Dijon) [1979] ECR 00649.

59 The table shows the frequency of collocates of effectiveness in the 1970s, 1980s, 1990s, and 2000s. The columns for each decade show the rank of the collocates, the frequency, and the t-score for every decade (columns from left to right). The first column for every decade indicates the rank of the collocate. Table 1 only visualizes the most frequent collocates and the words ‘supervision’ and ‘fiscal’ (most relevant for the first discussion) and also the words tax, evasion, avoidance, sixth, and VAT.

60 P. De Meo et al., ‘Generalized Louvain Method for Community Detection in Large Networks’, 11th International Conference on Intelligent Systems Design and Applications (ISDA) (2011), 88.

61 Case 8/74, Procureur du Roi v. Benoît and Gustave Dassonville, [1974] ECR 00837.

62 See De Meo et al., supra note 60.

63 See Skatteverket case, supra note 52.

64 Case 255/02, Halifax plc, Leeds Permanent Development Services Ltd and County Wide Property Investments Ltd v. Commissioners of Customs & Excise, [2006] ECR I-10609, at 121.

65 R. De La Feria and S. Vogenauer, Prohibition of Abuse of Law: A New General Principle of Eu Law? (2011), 636.

66 Ibid. Compare with the absence of comparable discussion in P. Craig and G. De Burca, EU Law: Text, Cases, and Materials (2011).

67 The CJEU held that in order to determine whether an abusive practice has taken place, two criteria had to be fulfilled: First, the transactions concerned, notwithstanding formal application of the conditions laid down by the relevant provisions of the Sixth Directive and the national legislation transposing it, resulted in the accrual of a tax advantage, the grant of which would be contrary to the purpose of those provisions. Second, it was apparent from a number of objective factors, such as the purely artificial nature of the transactions and the links between operators involved in the scheme, that the essential aim of those transactions concerned was to obtain a tax advantage. See Halifax case, supra note 64, paras. 74–81.

68 The red circles in Figure 3 are called centers of communities (in our case, they are represented as single cases). Their size is proportionate to the size of the communities that are formed in the entire case law citation network of the CJEU. The bigger the circle, the more cases belong to the same community, which is represented by an individual case as the center of the community. This is also the most cited case in the community.

69 Halifax case, supra note 64, para. 85.

70 Three networks in Figure 4 show the development of the case law: i) a decade after Marckx; ii) 20 years after; and iii) 34 years after (end of the network). The cases presented in the figure are connected to Marckx directly (meaning that they explicitly refer to Marckx) or indirectly (they cite cases which cite Marckx).The size and colour of the circles is proportionate to the number of citations they receive (in-degree) in a given period.

71 Marckx v. Belgium, Judgment of 13 June 1979, [1979] ECHR (Ser. A. no. 31), at 63.

72 Ibid., at 63.

73 James and Others v. the United Kingdom, Judgment of 21 February 1986, [1986] ECHR (Ser. A. no. 98).

74 Ibid., at 76.

75 Inze v. Austria, Judgment of 28 October 1987, [1987] ECHR (Ser. A. no. 126), at 43-45.

76 Karlheinz Schmidt v. Germany, Judgment of 18 July 1994, [1994] ECHR (Ser. A. no. 291-B), at 28.

77 Gaygusuz v. Austria, Judgment of 16 September 1996, [1996] ECHR (Reports 1996-IV), at 41.

78 Van Raalte v. the Netherlands, Judgment of February 21 1997, [1997] ECHR (Reports 1997-I), at 41.

79 See, e.g., D.J. Harris et al., Law of the European Convention on Human Rights (2014), 798 and 790.

80 Willis v. the United Kingdom, Judgment of 11 September 2002, [2002] ECHR (Reports 2002-IV), at 28.

81 Stec and Others v. the United Kingdom, Judgment of 12 April 2006, [2006] ECHR (Reports 2006-IV), at 42.

82 Ibid., at 66.

83 Andrejeva v. Latvia, Judgment of 18 February 2009, [2009] ECHR (Reports 2009), at 89.

84 N. Maccormick and R.S. Summers, Interpreting Precedents: A Comparative Study (1997), 454.

85 Case 166/78, Italian Republic v. Council of the European Communities (Premium for potato starch), [1979] ECR 2575, para. 8.

86 Derlén, M. and Lindholm, J., ‘Goodbye Van Gend En Loos, Hello Bosman? Using Network Analysis to Measure the Importance of Individual CJEU Judgments’, (2014) 20 European Law Journal 667 .

87 Clustering is a process in which similar vertices (which represent individual cases as dots in the network) form distinct groups by virtue of being more ‘similar’ to each other than they are to vertices in other groups. In social networks, most people interact with a small number of people most of the time, many of whom also know each other. See P.J. Carrington, J. Scott, and S. Wasserman, Models and Methods in Social Network Analysis (2005), 245. Yet surprisingly, the distance between people who do not know each other (who are not directly linked) is rather small. Cf. Small world phenomenon, six degrees of separation, ibid., at 246.

88 In this article we used the Louvain method, which is also the one that is used most commonly. For an overview of clustering techniques (physicists use the term community detection) see Fortunato, S., Community detection in graphs (2010) 486 Physics Reports 75174 . See also Section 3.

89 Alexy, R. and Peczenik, A., ‘The Concept of Coherence and Its Significance for Discursive Rationality’, (1990) 3 Ratio Juris 130 ; Alexy, R., ‘Coherence and Argumentation or the Genuine Twin Criterialess Super Criterion’, in Aarnio, A. et al. (eds.), On Coherence Theory of Law (1998 ).

90 D. Kennedy, A Critique of Adjudication: Fin De Siècle (1997), 424.

* Professor, European University Institute, Florence [].

** Professor, iCourts Centre of Excellence for International Courts, Copenhagen []. We thank Martin Christensen and Yannis Panagis for research assistance and data processing.

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