Book Review: Proportionality in Private Law. Ed. by Franz Bauer, Ben Koehler. -Tuebingen: Mohr Siebeck 2023. XIII, 219pp.

Abstract

In this book, containing papers from a conference held in Hamburg in May 2022, the editors sought to set out some preliminary steps in order to facilitate a comparative understanding of how proportionality works in private law settings. Accordingly, the contributions show the diversity of meanings and functions attached to the notion of proportionality. It would have gone beyond the scope of the book to explore how private law systems use proportionality to balance the interests of parties and of third parties or society as a whole. This would have been a particularly challenging endeavour, since there does not seem to be any general agreement about the definition and meaning of “proportionality” or of how it operates in legal reasoning in general or in private law in particular.
The terminology varies considerably depending on the jurisdiction, the field of law and the legal context. Only in European public law has the principle of proportionality become a term of art, referring to a specific three (or four)-prong test for judicial review of statutory provisions and government actions when they interfere with individual fundamental rights. The statutory provision or the action taken by the government has to serve a legitimate goal pursued by the empowering legislation, has to be suitable as well as necessary to achieve that goal, and must be proportionate stricto sensu, in that the disadvantages caused must not be disproportionate to the aims pursued. In other legal fields, proportionality may be used in a very broad sense associated with discretionary standards such as reasonableness or balancing. In the US, proportionality in public law is more akin to “interest balancing” or a rational means-end requirement, which means that as a term of art, it has acquired a different meaning there.
However, it cannot be said that the principle of proportionality in its European sense also applies in private law. In their contributions to this book, the authors had to redefine and re-conceptualize “proportionality”, in order to get the principle adapted to the framework of private law. There is not even a consensus as to which parts of the three-prong test are to be used in the different legal areas. All authors have also underlined the difficulties encountered due to the incommensurability of the factors relevant to the proportionality analysis in a private law setting in which the court is called upon to juggle the interests of parties, third parties and society in general.
The book seems to confirm the conclusions made by Oliver Remien in Max Planck Encyclopedia of European Private Law that, to the extent that national or EU private law provisions constitute a restriction of the fundamental freedoms, one may consider justifying them by reference to mandatory requirements of the public interest, but the justification must be compatible with the three-prong principle of proportionality. By contrast, it cannot be contended that the private law of the Member States irrespective of EU law, contains a proportionality principle as a yardstick for review of acts or omissions, for the lack of such a principle would erode private autonomy.
To sum up, the book is addressed to jurists and lawyers who wish to gain a better theoretical understanding of the principle of proportionality as well as its practical application by courts. Since a growing number of jurisdictions have shown interest in applying this principle and have used the terms “proportionate” and “disproportionate” in a variety of legal rules, its publication is commendable and timely.

Keywords: Proportionality, private law, constitutional law, administrative law, comparative law, EU Law, US Law, reasonableness, competition law, constitutional adjudication, fundamental human rights, litigation, procedural proportionality, legal remedies

JEL Classification: K