Universiteit Leiden

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Research programme

Coherent Private Law

How do national legislatures incorporate and embed the rules and principles that enter the private law system?

Tycho de Graaf

Coherency is a value in itself in national private law systems. Rules that citizens must observe on the grounds of a certain area of law, should ideally not be contradicted by rules from a different area of law. Guiding principles in one area of private law should also be guiding in other areas, unless there are good reasons to diverge from this. It is preferable that a legal definition applied in one area of private law is accorded the same meaning in other areas. These kinds of idealized system rules, which can be traced back to basic expectations with regard to predictability, clarity and enforceability of the private law system, are put to the test on a daily basis.

Constructing and reconstructing the Civil Code

The coherency of national private law systems and their doctrines are increasingly being put to the test as a result of all sorts of guidelines, regulations, treaties, codes and other influences outside private law. The consequences of this are felt directly and indirectly. Consequences for the ‘structure’ of the Netherlands Civil Code (BW) can be seen directly: it is constantly being constructed and reconstructed, often as a result of international developments. For example, important sections of property law in the BW have become binding in nature and originated at the European level; this gives rise to new questions regarding application and interpretation.

Rules of law from a higher level, that have to be incorporated in a national private law system often rub against self-evident basic principles such as freedom of contract, the division between property and contract law, or also when it comes to the national choice to codify certain matters in codes of law, but not to do so for other matters. Other areas of law within the national legal system, such as regulation via administrative law legislation, also have an impact. Whether this concerns family law, consumer protection, insolvency issues, personal injury or business administration, private law is a multilevel legal system where the traditional boundaries between public law and private law and also the boundaries between the law and other steering and structuring instruments are not only shifting, but are sometimes also blurred.

The expansion to include functional areas of the law such as financial law, insolvency law and child law as well as hybridisation in areas of law such as business law and family law demonstrate that private law and the coherence within it are not self-evident. These developments also require a review of the coherence i.e. the consistency and cohesion within private law. In certain areas of private law, the interwovenness of all these sources of law has become so prevalent that the question arises what the actual nature of private law is. How do national legislatures deal with these issues concerning coherence?

  • How do they view their task to incorporate and embed rules and principles that enter the realm of private law?
  • Are they able to create a coherent framework that strikes the right balance in order to facilitate social and economic interaction between businesses, consumers and families?
  • And how do these rules and principles find their way to the civil courts?

These are the issues that researchers on the Coherent Private Law programme are considering.

The main research questions of the programme are:

  1. What is the impact of European law, convention law and other fields of law (particularly administrative law) on private law?
  2. Hoe does private law deal with the interaction that arises from the impact of European law, convention law and other fields of law (particularly administrative law)?
  3. How should this interaction be assessed, in light of the interests involved in the regulations to be incorporated and in view of the function of private law in society?

The research programme Coherent Private Law has a clear link to the university profile area Interaction between Legal Systems, which conducts research into the connections and interaction between the different areas of the law and the various ‘layers’ of the legal order.

The research programme Coherent Private Law stems from the programme Vraagstukken van vermogensrecht (Issues of Property Law) (1997-2008). The main participants in the programme are researchers from the Institute of Private Law including the departments Civil Law (encompassing Civil Law, Civil Procedure Law and Private International Law),  Child Law, Financial Law (Hazelhoff Centre for Financial Law), Notarial Law and Business Law (encompassing Business Law/Insolvency Law and Intellectual Property Law), and also from the Department of Legal History of the Institute for the Interdisciplinary Study of the Law, the Department Business Studies from the Institute of Tax Law and Economics and legal economists from that Institute.

Academic Staff

PhD Candidates

External PhD Candidates


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