The Question of Case Selection in Comparative Constitutional Law

Although intellectual interest in the international migration of constitutional ideas has been growing steadily over the last decade, the field of comparative constitutional law remains under-theorized and lacks a coherent methodology. In fact, fundamental questions concerning the very purpose and rationale of comparative inquiry and how that enterprise is to be undertaken remain largely outside the purview of canonical constitutional law scholarship. Genuinely comparative, problem driven, and inference oriented scholarship is still difficult to come by. Most leading works in the field continue to lag behind the social sciences in their ability to trace causal links among pertinent variables, let alone to substantiate or refute testable hypotheses. More specifically, comparative constitutional law scholarship produced by legal academics often overlooks (or is unaware of) basic methodological principles of controlled comparison, research design, and case selection. The paper addresses this lacuna by contrasting the approaches of legal academics and political scientists to the same sets of comparative constitutional phenomena. The paper is divided into three main sections. I begin by identifying four main types of scholarship labeled as comparative in the field of constitutional law and politics: (i) freestanding, single-country studies mistakenly characterized as comparative only by virtue of dealing with any country other than the author's own; (ii) comparative reference aimed at self-reflection through analogy, distinction, and contrast; (iii) comparative research aimed at generating thick concepts and thinking tools through multi-faceted descriptions; and (iv) studies that draw upon controlled comparison and inference-oriented case selection principles in order to assess change, explain dynamics, and make inferences about cause and effect through systematic case selection and analysis of data. While the study of comparative constitutional law by legal academics has contributed significantly to concept formation and the accumulation of knowledge drawing upon the former three categories of comparative analysis, it has, for the most part, fallen short of advancing knowledge through inference oriented, controlled comparison. In the second part of the paper I discuss a few basic principles of case selection employed by inference-oriented studies in the field of comparative constitutional law and politics: (i) the most similar cases logic; (ii) the most different cases logic; (iii) the prototypical cases principle; (iv) the most difficult cases principle; and (v) the outlier cases principle. I subsequently illustrate the successful application of these principles by examining a few recently published and genuinely comparative works dealing with the foundations, practice, and consequences of constitutionalization worldwide. Problem driven and inference oriented comparative public law scholarship, I argue, should look more like these works. I conclude by suggesting that while there are many valuable approaches and methods to study comparative public law, the aspiration to make valid causal claims based on comparative research warrants adherence to inference-oriented principles of research design and case selection. Attention to, and reliance on, such inference-oriented principles of case selection may help scholars studying the migration of constitutional ideas to make valuable causal claims as to why, when, and how such migration is likely to occur. It would also allow the field as a whole to move beyond the multiple-description method commonly deployed in comparative legal analyses toward the next level of comparative inquiry: causal inference through controlled comparison.

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