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Precedent in International Courts: A Network Analysis of Case Citations by the European Court of Human Rights

  • Yonatan Lupu and Erik Voeten

Why and how do international courts justify decisions with citations to their own case law? We argue that, like domestic review courts, international courts use precedent at least in part to convince ‘lower’ (domestic) courts of the legitimacy of judgements. Several empirical observations are consistent with this view, which are examined through a network analysis of European Court of Human Rights (ECtHR) citations. First, the Court cites precedent based on the legal issues in the case, not the country of origin. Second, the Court is more careful to embed judgements in its existing case law when the expected value of persuading domestic judges is highest. These findings contribute to a developing literature that suggests international and domestic review courts develop their authority in similar ways.

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1 Fowler, James H., Johnson, Timothy R., Spriggs, James F. II, Sangick Jeon and Wahlbeck, Paul J., ‘Network Analysis and the Law: Measuring the Legal Importance of Supreme Court Precedents’, Political Analysis, 15 (2007), 324346; Fowler, James H. and Sangick Jeon, ‘The Authority of Supreme Court Precedent’, Social Networks, 30 (2008), 1630; Bommarito, Michael, Katz, Daniel and Zelner, Jonathan, ‘On the Stability of Community Detection Algorithms for Longitudinal Citation Data’, Proceedings of the 6th Conference on Applications of Social Network Analysis (ASNA) (2009).

2 See, for example, Majone, Giandomenico, ‘Two Logics of Delegation: Agency and Fiduciary Relations in EU Governance’, European Union Politics, 2 (2001), 103122; Alter, Karen J., ‘Agents or Trustees? International Courts in Their Political Context’, European Journal of International Relations, 14 (2008), 3363.

3 Garrett, Geoffrey and Weingast, Barry, ‘Ideas, Interests and Institutions: Constructing the EC's Internal Market’, in Judith Goldstein and Robert O. Keohane, eds, Ideas and Foreign Policy (Ithaca, NY: Cornell University Press, 1993); Garrett, Geoffrey, Kelemen, Daniel and Schulz, Heiner, ‘The European Court of Justice, National Governments and Legal Integration in the European Union’, International Organization, 52 (1998), 149176; Stephan, Paul B., ‘Courts, Tribunals and Legal Unification – The Agency Problem’, Chicago Journal of International Law (2002), 333352; Carrubba, Clifford, Gabel, Matthew and Hankla, Charles, ‘Judicial Behavior under Political Constraints: Evidence from the European Court of Justice’, American Political Science Review, 102 (2008), 435452.

4 See, for example, Busch, Marc, ‘Overlapping Institutions, Forum Shopping, and Dispute Settlement in International Trade’, International Organization, 61 (2007), 735761; Helfer, Laurence R., ‘Nonconsensual International Lawmaking’, University of Illinois Law Review, 71 (2008), 71125.

5 See, for example, Epstein, Lee and Knight, Jack, The Choices Justices Make (Washington, DC: CQ Press, 1998).

6 Poole, Keith T. and Howard Rosenthal, ‘D-NOMINATE after 10 Years: A Comparative Update to Congress: A Political-Economic History of Roll Call Voting’, Legislative Studies Quarterly, 26 (2001), 529.

7 Lupu, Yonatan and Fowler, James H., ‘Strategic Citations to Precedent on the U.S. Supreme Court’ (unpublished, University of California-San Diego, 2011, available at

8 See, for example, Alec Stone Sweet, ‘On the Constitutionalization of the Convention: The European Court of Human Rights as a Constitutional Court’, Revue trimestrielle des droits de l'homme, 80 (2009), 923944.

9 See, for example, Alter, Karen J., The European Court's Political Power: Selected Essays (Oxford: Oxford University Press, 2009); Staton, Jeffrey K. and Moore, Will H., ‘Judicial Power in Domestic and International Politics’, International Organization, 65 (2011), 553587; Voeten, Erik, ‘The Impartiality of International Judges: Evidence from the European Court of Human Rights’, American Political Science Review, 102 (2008), 417433.

10 The twenty-seven EU members and Albania, Andorra, Armenia, Azerbaijan, Bosnia and Herzegovina, Croatia, Georgia, Iceland, Liechtenstein, Moldova, Monaco, Montenegro, Norway, Russia, San Marino, Serbia, Switzerland, the former Yugoslav Republic of Macedonia, Turkey and Ukraine.

11 Voeten, ‘The Impartiality of International Judges’.

12 Although Article 38 allows judicial decisions to be a ‘subsidiary means for the determination of the rules of law’.

13 Shahabuddeen, Mohammed, Precedent in the World Court (Cambridge: Cambridge University Press, 2007).

14 Busch, ‘Overlapping Institutions, Forum Shopping, and Dispute Settlement in International Trade’.

15 13 August 1981, Young, James and Webster v. The United Kingdom. More generally, the ‘orthodox view’ is that a state ‘is obliged to observe only those judgements made directly against it’. See Greer, Steven, The European Convention on Human Rights: Achievements, Problems and Prospects (Cambridge: Cambridge University Press, 2006), p. 279.

16 Wildhaber, Luzius, ‘Precedent in the European Court of Human Rights’, in Paul Mahoney, ed., Protection des droits de l'homme: la perspective européenne, mélanges à la mémoire de Rolv Ryssdal (Cologne: Heymann, 2000), pp. 15291545.

17 Busch, ‘Overlapping Institutions, Forum Shopping, and Dispute Settlement in International Trade’.

18 Carrubba et al., ‘Judicial Behavior under Political Constraints’.

19 Recent examples are cases on the extradition of suspected terrorists to countries where they might be tortured (e.g. Ramzy v. Netherlands, Chahal v. The United Kingdom, and Saadi v. Italy).

20 Most ECtHR judgements on the merit are reached by panels of seven judges. Some cases are referred to the seventeen-judge Grand Chamber.

21 See, for example, John Henry Merryman, ‘The Authority of Authority: What the California Supreme Court Cited in 1950’, Stanford Law Review, 6 (1954), 613673; Harris, Peter, ‘Difficult Cases and the Display of Authority’, Journal of Law, Economics & Organization, 1 (1985), 209221; Tyler, Tom R. and Gregory Mitchell, ‘Legitimacy and the Empowerment of Discretionary Legal Authority: The United States Supreme Court and Abortion Rights’, Duke Law Journal, 43 (1994), 703815; 817–44; Corley, Pamela C., Howard, Robert M. and Nixon, David C., ‘The Supreme Court and Opinion Content: The Use of the Federalist Papers’, Political Research Quarterly, 58 (2005), 329340; Hansford, Thomas G. and Spriggs, James F. II, The Politics of Precedent on the U.S. Supreme Court (Princeton, NJ: Princeton University Press, 2006); Hume, Robert J., ‘The Use of Rhetorical Sources by the U.S. Supreme Court’, Law & Society Review, 40 (2006),817844.

22 See, for example, Carrubba et al., ‘Judicial Behavior under Political Constraints’; Cichowski, Rachel A., The European Court and Civil Society: Litigation, Mobilization, and Governance (Cambridge: Cambridge University Press, 2007); Helfer, Laurence R. and Anne-Marie Slaughter, ‘Why States Create International Tribunals: A Response to Professors Posner and Yoo’, California Law Review, 93 (2005), 899956.

23 Hume, ‘The Use of Rhetorical Sources by the U.S. Supreme Court’.

24 Bailey, Michael A. and Forrest Maltzman, ‘Does Legal Doctrine Matter? Unpacking Law and Policy Preferences on the U.S. Supreme Court’, American Political Science Review, 102 (2008), 369384.

25 See, for example, Ethan Bueno de Mesquita and Stephenson, Matthew, ‘Informative Precedent and Intrajudicial Communication’, American Political Science Review, 96 (2002), 755766.

26 See, for example, Lax, Jeffrey R. and Cameron, Charles M., ‘Bargaining and Opinion Assignment on the US Supreme Court’, Journal of Law, Economics & Organization, 23 (2007), 276302; Lupu and Fowler, ‘Strategic Citations to Precedent on the U.S. Supreme Court’.

27 Slaughter, Anne-Marie, ‘A Global Community of Courts’, Harvard International Law Journal, 44 (2003), 191219, p. 192. Sociologists have long analysed the ‘juridical field’ in this way, inspired by the work of Bourdieu; see Bourdieu, Pierre, ‘The Force of Law: Toward a Sociology of the Juridical Field’, Hastings Law Journal, 38 (1987), 814853. This approach stresses that there are unique qualities that separate legal practice from other social activities but that the field is not a self-contained system, autonomous from the political and social realms.

28 Shapiro, Martin, Courts: A Comparative and Political Analysis (Chicago: University of Chicago Press, 1981).

29 Alec Stone Sweet, ‘On the Constitutionalization of the Convention’, p. 1.

30 Similar arguments have been advanced in the context of the European Court of Justice (ECJ). See, for example, Weiler, Joseph, ‘A Quiet Revolution: The European Court of Justice and its Interlocutors’, Comparative Political Studies, 26 (1994), 510534.

31 See, for example, Helfer, Laurence R. and Anne-Marie Slaughter, ‘Toward a Theory of Effective Supranational Adjudication’, Yale Law Journal, 107 (1997), 273391.

32 Hillebrecht, Courtney, ‘The European Court of Human Rights, Domestic Politics and the Ties that Bind: Explaining Compliance with International Human Rights Tribunals’ (doctoral dissertation, University of Wisconsin, Madison, 2010); Andreas Von Staden, ‘Shaping Human Rights Policy in Liberal Democracies: Assessing and Explaining Compliance with the Judgements of the European Court of Human Rights’ (doctoral dissertation, Princeton University, 2009).

33 Supervision of the Execution of Judgements of the European Court of Human Rights, 3rd Annual Report, p. 51.

34 Supervision of the Execution of Judgements, p. 63. A final resolution is adopted by the Committee of Ministers when it is satisfied that a government has implemented an ECtHR judgement.

35 Supervision of the Execution of Judgements, p. 7.

36 See, for example, Keller, Helen and Alec Stone Sweet, A Europe of Rights: The Impact of the ECHR on National Legal Systems (Oxford University Press, 2008).

37 ECtHR, judgement of 24 July 2003, Karner v. Austria.

38 Claes, Monica, The National Courts’ Mandate in the European Constitution (Oxford: Hart, 2006).

39 Chester v. Secretary of State for Justice & Another [2010] EWCA Civ 1439 (17 December 2010).

40 See, for example, Keller and Stone Sweet, A Europe of Rights.

41 Harris, , ‘Difficult Cases and the Display of Authority’, pp. 209–10. See also Hume, ‘The Use of Rhetorical Sources by the U.S. Supreme Court’.

42 Troper, Michael and Grzegorczyk, Christophe, ‘Precedent in France’, in D. Neil MacCormick and Robert S. Summers, eds, Interpreting Precedents: A Comparative Study (Aldershot, Surrey: Ashgate Publishing, 1997); Powell, Emilia J. and Mitchell, Sara M., ‘The International Court of Justice and the World's Three Legal Systems’, Journal of Politics, 69 (2007), 397415.

43 This logic can be further explained by way of analogy. Suppose that scientific articles within a given field tend to cite other articles within the same field more often than not (e.g., political science articles cite other political science articles, etc.). As the network of academic citations develops, therefore, communities of papers will form based on the academic field because those papers tend to cite each other more than they cite papers in other fields (and therefore other communities).

44 Lasser, Mitchell, Judicial Deliberations. A Comparative Analysis of Judicial Transparency and Legitimacy (Oxford: Oxford University Press, 2004), p. 298.

45 Merryman, , ‘The Authority of Authority’, pp. 1–2. Also quoted in Sara McLaughlin Mitchell and Emilia Justyna Powell, Domestic Law Goes Global: Legal Traditions and International Courts (Cambridge: Cambridge University Press, 2011).

46 McLaughlin Mitchell and Powell, Domestic Law Goes Global.

47 Gerards, Janneke H., ‘Judicial Deliberations in the European Court of Human Rights’, in N. Huls, M. Adams and J. Bomhoff, eds, The Legitimacy of Highest Courts’ Rulings (The Hague: T. M. C. Asser Institute, 2008); Gerards, Janneke H., ‘Pluralism, Deference and the Margin of Appreciation Doctrine’, European Law Journal, 17 (2011), 80120.

48 Gerards, ‘Judicial Deliberations in the European Court of Human Rights’.

49 Sweeney, James A., ‘Margins of Appreciation: Cultural Relativity and the European Court of Human Rights in the Post-Cold War Era’, International & Comparative Law Quarterly, 54 (2005), 459474.

50 See, for example, Howard Charles Yourow, The Margin of Appreciation Doctrine in the Dynamics of European Human Rights Jurisprudence (Leiden: Martinus Nijhoff, 1995).

51 Gerards, ‘Judicial Deliberations in the European Court of Human Rights’.

52 This figure includes only judgements on the merits.

53 See, for example, Fowler et al., ‘Network Analysis and the Law’.

54 Approximately 15.6 per cent of the ECtHR decisions are outside the main cluster (compared with 16.2 per cent in the USSC's network). Cases that cite no precedent would all have hub scores of zero. The Tobit model we use in our analysis is designed to address the fact that we have excluded such cases from our sample.

55 The excluded cases are those designated importance level 3 by the Court.

56 This article is only invoked in conjunction with other Convention rights, limiting its application since the Convention includes no socio-economic rights other than education. The optional Protocol 12 remedies this but is ratified by less than half of Council of Europe member states.

57 Fowler et al., ‘Network Analysis and the Law’.

58 For USSC citations, we use the data provided by Fowler and Jeon, ‘The Authority of Supreme Court Precedent’. The citations follow patterns common in large-scale networks, including scientific citation networks (see Albert, Reka and Barabási, Albert-Laszlo, ‘Statistical Mechanics of Complex Networks’, Reviews of Modern Physics, 74 (2002), 4797; Boerner, Katy, Maru, Jeegar T. and Robert L., Goldstone, ‘The Simultaneous Evolution of Author and Paper Networks’, Proceedings of the National Academy of Sciences, 101 (2004), 52665273; Borgatti, Stephen P. and Everett, Martin G., ‘Models of Core/Periphery Structures’, Social Networks, 21 (1999), 375395)). In both courts, the patterns of inward citations closely resemble the power-law distribution of other complex networks, often referred to as scale-free networks, including the World Wide Web ( Albert, Reka, Jeong, Hawoong and Albert-Laszlo Barabási, ‘The Diameter of the World Wide Web’, Nature, 401 (1999), 130131) and social networks ( Ebel, Holger, Mielsch, Lutz-Ingo and Bornholdt, Stefan, ‘Scale-free Topology of e-mail Networks’, Physical Review E, 66 (2002), 035103-14. Network theorists argue that this distribution results from a process called ‘preferential attachment’ (Albert-Laszlo Barabási and Reka Albert, ‘Emergence of Scaling in Random Networks’, Science, 286 (1999), 509–12), which in this context suggests that the more often a case has been cited in this past, the higher the probability that it will be cited in new cases.

59 Fowler et al., ‘Network Analysis and the Law’; Fowler and Jeon, ‘The Authority of Supreme Court Precedent’.

60 The Protocol went into force on 1 November 1998.

61 Fowler et al., ‘Network Analysis & the Law’; Fowler and Jeon, ‘The Authority of Supreme Court Precedent’.

62 Kleinberg, Jon M., ‘Authoritative Sources in a Hyperlinked Environment’, Journal of the Association for Computing Machinery, 46 (1999), 604632.

63 Fowler and Jeon, ‘The Authority of Supreme Court Precedent’.

64 The Grand Chamber of seventeen judges takes cases it deems important directly and also reviews some decisions by the regular seven-judge Chambers, usually at the request of respondent governments.

65 For similar approaches, see Lupu and Fowler, ‘Strategic Citations to Precedent on the U.S. Supreme Court’; Cross, Frank B., Spriggs, James F. II, Johnson, Timothy R. and Wahlbeck, Paul J., ‘Citations in the U.S. Supreme Court: An Empirical Study of their Use and Significance’, University of Illinois Law Review (2010), 489576.

66 Note that many of our country-specific variables are relatively fixed, thus making it impossible to have fixed effects and the country variables in the model at the same time.

67 Rafael La Porta, López-de-Silanes, Florencio, Shleifer, Andrei and Vishny, Robert W., ‘Law and Finance’, Journal of Political Economy, 106 (1998), 11131155.

68 Heston, Alan, Summers, Robert and Aten, Bettina, Penn World Table Version 6.3 (Center for International Comparisons of Production, Income and Prices at the University of Pennsylvania, August 2009).

69 Marshall, Monty G. and Keith Jaggers. Polity IV Project: Political Regime Characteristics and Transitions, 1800–2009 (College Park.: Center for International Development and Conflict Management, University of Maryland, 2009).

70 Coded to increase with greater respect for these rights.

71 Tobin, James, ‘Estimation for Relationships with Limited Dependent Variables’, Econometrica, 26 (1958), 2436.

72 We estimated these models using robust standard errors clustered on the respondent country.

73 Imai, Kosuke, King, Gary and Lau, Olivia, Zelig: Everyone's Statistical Software (2009), available at

74 Powell, Emilia J. and Staton, Jeffrey K., ‘Domestic Judicial Institutions and Human Rights Treaty Violation’, International Studies Quarterly, 53 (2009), 149174.

75 Neal Tate, C. and Linda Camp Keith, ‘Conceptualizing and Operationalizing Judicial Independence Globally’ (paper prepared for the Annual Meeting of the American Political Science Association, Chicago, 2007.

76 Gibney, Mark, ‘Political Terror-Scores 1980–2002’ (2003), available at (accessed 4 February 2010).

77 Porter, Mason A., Jukka-Pekka Onnela and Mucha, Peter J., ‘Communities in Networks’, Notices of the American Mathematical Society, 56 (2009), 10821097; Costa, Luciano da F., Rodrigues, Francisco A., Gonzalo Travieso and P. R. Villas Boas, ‘Characterization of Complex Networks: A Survey of Measurements’, Advances in Physics, 56 (2007), 167242; Newman, Mark E. J., ‘Fast Algorithm for Detecting Community Structure in Networks’, Physical Review E, 69 (2004), 066133-1–5.

78 Newman, Mark E. J., ‘Modularity and Community Structure in Networks’, Proceedings of the National Academy of Sciences, 103 (2006), 85778582.

79 Porter, Mason A., Mucha, Peter J., Newman, Mark E.J. and Warmbrand, Casey M., ‘A Network Analysis of Committees in the United States House of Representatives’, Proceedings of the National Academy of Sciences, 102 (2005), 70577062.

80 Waugh, Andrew S., Liuyi Pei, Fowler, James H., Mucha, Peter J. and Porter, Mason A., ‘Party Polarization in Congress: A Social Network Approach’ (unpublished paper, University of California-San Diego, 2009).

81 Zhang, Yan, Friend, A. J., Traud, Amanda L., Porter, Mason A., Fowler, James H. and Mucha, Peter J., ‘Community Structure in Congressional Cosponsorship Networks’, Physica A, 387 (2008), 17051712.

82 Newman, ‘Fast Algorithm for Detecting Community Structure in Networks’. Because this type of algorithm can be sensitive to implementation details, we note that we used the software package igraph, version 0.54, in the R programming language ( Csardi, Gabor and Nepusz, Tamas, ‘The igraph Software Package for Complex Network Research’, InterJournal Complex Systems (2006), 1695).

83 In the only other paper we are aware of that used community detection algorithms on a network of judicial citations, Bommarito et al. found that the Newman method produced stable results when used on the network of USSC citations. They also found that this stability increased when using a smaller portion of the network, which is encouraging to our research, because the ECtHR network is significantly smaller than the USSC network (Bommarito et al., ‘On the Stability of Community Detection Algorithms for Longitudinal Citation Data’).

84 Djankov, Simeon, La Porta, Rafael, López de Silanes, Florencio and Shleifer, Andrei, ‘Courts’, Quarterly Journal of Economics, 118 (2003), 453517.

85 Voeten, ‘The Impartiality of International Judges’.

86 Helfer, ‘Nonconsensual International Lawmaking’.

87 Busch, ‘Overlapping Institutions, Forum Shopping, and Dispute Settlement in International Trade’.

88 See, for example, Dorussen, Han and Ward, Hugh, ‘Intergovernmental Organizations and the Kantian Peace’, Journal of Conflict Resolution, 52 (2008), 189–21; Hafner-Burton, Emilie M., Miles Kahler and Montgomery, Alexander H., ‘Network Analysis for International Relations’, International Organization, 63 (2009), 559592.

89 Zaring, David, ‘The Use of Foreign Decisions by Federal Courts: An Empirical Analysis’, Journal of Empirical Legal Studies, 3 (2006), 297331.

* Department of Political Science, University of California–San Diego (email: ); and Edmund A. Walsh School of Foreign Service and Government Department, Georgetown University (email: ), respectively. This research was supported in part by the Laboratory on International Law and Regulation at UCSD. Earlier versions of this article were presented at the University of California–San Diego, Cornell University, the 2010 International Studies Association Annual Convention, the 2010 Political Networks Conference, the 2010 American Political Science Association Annual National Conference, and the 2010 Pan-European Conference on International Relations. The authors wish to thank the participants in these seminars, and also Eyal Benvenisti, Mike Bommarito, Anna Dolidze, Asif Efrat, Chris Fariss, James Fowler, Larry Helfer, Dan Katz, Daniel Klerman, Sarah Kreps, David Lake and Mitchel Lasser for useful comments and suggestions.

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