Contact Me | Impressum

Prof. Dr. Niels Petersen
Lehrstuhl für öffentliches Recht, Völker- und
Europarecht sowie empirische Rechtsforschung
Universitätsstr. 14-16
48143 Münster

Tel.: +49-251-83-22021

E-mail: niels.petersen [at]

Webpage of the professorship | Webseite des Lehrstuhls


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Monograph: Proportionality and Judicial Activism

The principle of proportionality is one of the hottest topics in the field of comparative constitutional law at the moment. Many critics claim that courts use the proportionality test as an instrument of judicial self-empowerment. The book tests this hypothesis empirically. For this purpose, it systematically analyses the fundamental rights jurisprudence of the Canadian Supreme Court, the German Federal Constitutional Court, and the South African Constitutional Court. While the proportionality test gives judges a considerable amount of discretion, the study shows that this analytical openness does not necessarily lead to judicial activism. Instead, judges face significant institutional constraints. Because of these constraints, all three analysed courts refrain from using proportionality for purposes of judicial activism.

Publisher: Cambridge University Press

Year of publication: 2017

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Article: The International Court of Justice and the Judicial Politics of Identifying Customary International Law

It is often observed in the literature on customary international law that the identification practice of the International Court of Justice for customary norms deviates from the traditional definition of custom in Art. 38 (1) lit. b of the ICJ Statute. However, while there are many normative and descriptive accounts on customary law and the Court's practice, few studies try to explain the jurisprudence of the ICJ. This study aims at closing this gap. I argue that the ICJ's argumentation pattern is due to institutional constraints the Court faces. In order for its decisions to be accepted, it has to signal impartiality through its reasoning. However, the analysis of state practice necessarily entails the selection of particular instances of practice, which could tarnish the image of an impartial court. In contrast, if the Court resorts to the consent of the parties or widely accepted international documents, it signals impartiality.

Published in: European Journal of International Law, Vol. 28 (2017), pp. 357-385

Article: Avoiding the Common Wisdom Fallacy

More than one hundred years ago, the U.S. Supreme Court started to refer to social science evidence in its judgments. However, this has not resonated with many constitutional courts outside the United States, in particular in continental Europe. This study has a twofold aim. First, it tries to show that legal reasoning in constitutional law is often based on empirical assumptions so that there is a strong need for the use of social sciences. However, constitutional courts often lack the necessary expertise to deal with empirical questions. Therefore, the study discusses three potential strategies to make use of social science evidence. Judges can interpret social facts on their own, they can afford a margin of appreciation to the legislature, or they can defer the question to social science experts. It will be argued that none of these approaches in itself is satisfactory so that courts will have to employ a combination of different strategies. In order to illustrate the argument, I will discuss decisions of different jurisdictions, including the United States, Canada, Germany, and South Africa.

Published in: International Journal of Constitutional Law, Vol. 11 (2013), pp. 294-318 (free)


Article: Legislative Inconsistency and the "Smoking Out" of Illicit Motives

The study analyzes consistency arguments that are common in the case law of several courts relying on the proportionality principle in their individual rights jurisprudence. It examines cases from five different constitutional or supreme courts, arguing that the main function of consistency considerations is the “smoking out” of illicit motives. Legislative inconsistency is an indication that the legislature also pursued different aims than the ones which were stated explicitly. The parliamentary majority may have been captured by interest groups, or it might have had incentives to discriminate against societal minorities. This hypothesis is confirmed by the analyzed cases. While courts are not able to control the motives of the legislature directly, consistency considerations provide indications for legislative motivation.

Published in: American Journal of Comparative Law, Vol. 64 (2016), pp. 121-145

Working Paper version on SSRN

Article: The German Constitutional Court and Legislative Capture

Political decision-making is often influenced through the lobbying of strong interest groups. This is not per se a problem for democracy. It becomes a problem if political decisions are primarily motivated by the intention to grant certain interest groups a favor. This contribution deals with the question whether constitutional courts can play a role in remedying this pathology of the political process. It has a normative and a reconstructive dimension. The normative part makes a case that constitutional courts should police interest group capture. However, the direct control of legislative motivation is an impossible task. For this reason, constitutional courts should recur to second-order criteria, which focus on the rationality of the legislation. If legislation lacks a tight means-end fit or is inconsistent, this is an indication that the legislature has pursued not only public-regarding aims. The reconstructive part analyzes the jurisprudence of the German Constitutional Court. In several judgments, the German Constitutional Court made allusions to a potential capture of the legislature. However, it never relied on legislative motivation to justify its decisions. Instead, it performed a rationality review and found that the legislation in question was either inconsistent or disproportionate. The contribution thus offers a new perspective on the traditional doctrines of proportionality and inconsistency. Even though these doctrines allow prima facie for a rationality review of the legislature, they can also be used to flush out illicit legislative motivations.

Published in: International Journal of Constitutional Law, Vol. 12 (2014), pp. 650-669

Article: Antitrust Law and the Promotion of Democracy and Economic Growth

There is a considerable debate in the legal literature about the purpose of antitrust institutions. Some argue that antitrust law merely serves the purpose of economic growth, while others have a broader perspective on the function of antitrust, maintaining that the prevention of economic concentration is an important means to promote democratization and democratic stability. This contribution seeks to test the empirical assumptions of this debate. Using panel data of 154 states from 1960 to 2005, it analyzes whether antitrust law actually has a positive effect on democracy and economic growth. The paper finds that antitrust law has a positive effect on the level of GDP per capita and economic growth after ten years. However, there is no significant positive effect on the level of democracy. It is suggested that these results might be due to the current structure of existing antitrust laws, which are designed to promote economic efficiency rather than to prevent economic concentration.

Published in: Journal of Competition Law & Economics, Vol. 9 (2013), pp. 593-636

Working Paper version on SSRN

Article: Determining the Domestic Effect of International Law through the Prism of Legitimacy

Traditional theory on the relationship between international law and domestic legal orders distinguishes between monist and dualist systems: those that accept the primacy of international law over domestic law, and those that do not attribute direct effect to international law in the domestic legal order. It is argued that this distinction has little explanatory value when it comes to the implementation of decisions of international courts or institutions. All courts dealing with the domestic effect of international secondary law ultimately face questions of legitimacy of the external decision-making process. I analyze the jurisprudence of three different constitutional courts on the effect of decisions of international authorities in the domestic order. These courts are the US Supreme Court, the European Court of Justice, and the German Constitutional Court. It will be argued that each of these courts applies a different strategy to cope with the challenge of legitimacy of international decision-making. Therefore, it seems to be more appropriate to consider the relationship of a national legal order to international law through the prism of how its constitutional court approaches the governance issue, rather than referring to the traditional monism-dualism dichotomy.

Published in: Zeitschrift für ausländisches öffentliches Recht und Völkerrecht, Band 72 (2012), S. 223-259 (free)

Article: Customary Law without Custom

The role of state practice in the formation of unwritten international law has attracted a lot of attention in recent decades. According to the traditional view, state practice is one of the two constituent elements of customary international law. In practice, its importance is however decreasing. Modern international law scholarship increasingly turns to interpretative methods when identifying customary law. In this process, international courts and tribunals as well as international law scholars only pay lip service to state practice. The study analyzes this development and proposes to distinguish two types of unwritten norms. On the one hand, there is customary law, which still requires the evidence of state practice as a constituent element. On the other hand, however, there are general principles. These general principles can be identified by the mere recurrence to opinio juris. The distinction between both types of norms is based on a classification drawn from legal theory. This classification distinguishes conduct-related rules from interest-related principles. While the former are to be seen as customary norms in the traditional sense, the latter may be qualified as general principles.

Published in: American University International Law Review, Vol. 23 (2008), pp. 275-310 (free)

Textbook: Economic Methods for Lawyers

(with Emanuel Towfigh)

Economic reasoning has become more and more important in legal scholarship. However, transplanting economic arguments into legal thought is not straightforward. While the results of economic studies may often seem straightforward, it is, however, often impossible to derive adequate conclusions for legal arguments without understanding the methodological limitations and caveats. This book intends to close this gap. Unlike many other Law & Economics textbooks, it does not offer an analysis of particular areas of law from an economic perspective. Instead, it gives an introduction to the tools that economists use in order to enable law students, legal scholars and practitioners better to understand economic studies and to use them for their own legal reasoning. To achieve this aim, it deals with different topics of economic methodology and economic thinking, such as game theory, public choice and social choice theory, behavioural economics, empirical research design, and basic statistics.

Publisher: Edward Elgar

Year of publication: 2015

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