Contemporary national legal systems are exposed to numerous influences and many of them push towards a more casuistic, detailed and comprehensive regulation. It might appear at first sight that such a form of regulation is less ambiguous for its addressees, because specific provisions better indicate what rights and obligations are thus vested in individuals. This would be true only if the law directly envisaged the specific situations to which it ought to be applied. However, legal regulation – by its very nature – concerns not individually specified persons, but rather certain types of addressees, and the rights and obligations are also defined in a general way. It follows from the above, among other things, that it is not purposeful for the law to go into specific details when describing all the situations that may occur in reality. On the contrary, highly differentiated and comprehensive legislation becomes an obstacle to determining what specific rights and obligations should apply in situations that are not directly regulated by the law. If we are to infer from an incomplete legal regulation what rights and obligations are applicable in any given situation, we have to embrace new arguments following from the legal order as a whole rather than from the specific legal rule. These new rules may take the form of abstract legal principles, expressions of values recognised by the law or purposes of the relevant legal regulation. However, it might be difficult to identify these often unwritten rules. Thus, differentiation of the law in fact reveals the issue of ensuring the coherence of the whole legal system.

The Czech Republic – as a medium-sized country in Central Europe which transformed its legislation during its democratic transition after 1990 – can serve as an example in this respect. Three distinct legal systems have been applicable in its territory since 2004, when the country joined the European Union (EU): (i) national law; (ii) EU law and (iii) to a certain extent also public international law, in view of the incorporation of international treaties and the effects of other rules of public international law in the national legal system.