Although the concept of hard law and soft law belongs to subjects that appeared in the doctrine of international law more than 30 years ago, it is still one of the complex and controversial issues. This is not merely because of the conflict of different theories of international law, in particular positivist approaches which mostly refuse the concept of soft law as a kind of law of lower degree, on the one hand, and anti-positivist theories which took much more conciliatory or even supportive standpoint to this concept, on the other hand.
The key issue is that the doctrine, which feels a lack of more appropriate terms and aims at generalization, started to use the term of soft law for two very different phenomena: first, for such documents that do not lack a legally binding form but have, fully or partly, soft formulation, i.e. weak, general or non-normative obligations (negotium), second, for rules that lack a due legal form (instrumentum). Mainly the second case, i.e. rules with a soft instrumentum (various resolutions of international organizations and conferences), means a greater legal and political problem.
However, the international legal doctrine is not to be blamed that it would introduce the concept of soft law in order to extend artificially its field of study. On the contrary, the doctrine has just reacted to a phenomenon that emerged as a consequence of law-making activities of states and international organizations. Its task is to analyze and to name it. One can only have some doubts whether the ambiguous term of soft law is an adequate tool for understanding and interpretation of two substantially different phenomena in contemporary international law.