Soft Law's Journey: A Tale of Blurred Lines and Complex Governance

This post, authored by Felix Schott, is part of a series of external posts building on the 2025 BIICL-SLS Workshop which this year focused on soft law in international law. Between December 2025 and February 2026, we will be publishing posts addressing different aspects of soft law, including its conceptualisation and role, its application in different areas of law, and its influence in particular domestic contexts. The posts in this series are by external authors, and whilst BIICL has undertaken a review, they do not necessarily reflect the views of BIICL or its team members.

In recent years, "soft law" has become somewhat of a catchphrase in international (legal) parlance. Depending on the circumstances, the term is used to refer to a wide array of international instruments with different degrees of normativity, stemming from different institutional backgrounds and trying to achieve different results. These instruments sometimes share little but the fact that they are said to have some sort of normative effect despite not forming part of binding international law as it is reflected in Article 38 of the ICJ Statute. The growing interest in soft law notwithstanding, there continues to exist an inherent lack of clarity in the concept. How "soft" is it? What is "it"? And is it law?

This blog post attempts to shed some light on the term by briefly retracing three key stages of development in the conceptual journey of soft law in international law. It mainly uses formal and informal instruments or agreements as opposing terms of analysis, as this distinction focusses on how a soft law instrument's origins differ from traditional international law-making and does not prejudge the question of a given instrument's precise legal status without having properly analysed its (in-)direct legal effects. My aim here is of course not to provide a comprehensive history of soft law, but merely to show that our understanding of what it constitutes has changed considerably over time. Highlighting the changeability of the term invites further reflection on the precise contours and effects of what we often fleetingly refer to as "soft law".

Early signs of soft law forming as a new category of international instruments

While the term "soft law" in its current meaning is commonly - though perhaps wrongly - attributed to McNair (see n 32), I would argue that we can identify even earlier signs of a category of soft law forming in international legal discourse. A good starting point in that regard is early scholarly works on non-treaty instruments. Already in the 1920s, Jean Basdevant explored a wide range of diplomatic instruments with direct or indirect legal significance in his Hague lectures entitled "La conclusion et la rédaction des traités et des instruments diplomatiques autres que les traités". The legal assessment of some of his examples seems rather straightforward: for instance, it is quite clear that records of a treaty conference may have indirect legal significance as travaux préparatoires in the later interpretation of the treaty. These kinds of examples nonetheless show that non-treaty instruments at the time began to receive more attention from the perspective of international law, albeit still largely without according them a normative, law-like effect of their own. However, Basdevant also discusses two categories of non-treaty instruments that are more difficult to explain from a traditional perspective:

• Instruments adopted by a commission set up by two or more states with a view to preparing or taking certain decisions, such as instruments by international river commissions, as well as
• accords administratifs, which he describes as instruments of a lesser diplomatic character, "no longer adopted by those whose normal mission it is to represent the state abroad, but drawn up and signed by technical functionaries instead", such as agreements on the development of postal or telephone services.

Basdevant's scholarship, taken together with other examples such as Ludwig Bittner's "Die Lehre von den völkerrechtlichen Vertragsurkunden" ("The doctrine of international treaty documents", 1924), goes to show that, already in the 1920s, one ran into significant difficulties when trying to explain existing international practice solely by reference to formal international agreements. In fact, a wide variety of non-treaty instruments of varying legal significance were already being used, which can be seen as early signs of a category of soft law instruments developing. However - and this is perhaps an aspect that still distinguishes the practice of the 1920s from today's - most non-treaty instruments at the time were accorded only quite limited normative value of their own, if any at all. Therefore, despite the diversification of international instruments, the dividing line between law and non-law was still quite visible at the time. That being said, instruments like the ones adopted by international river commissions or the accords administratifs already foreshadow the growing complexification of international governance that came with increased institutionalisation at the international level and the corresponding need to resort to other, more flexible instruments in addition to formal international agreements.

The rise of international organisations: Proliferation and diversification of soft law

Indeed, the establishment of modern international organisations and their ensuing activities in many (new) subject areas of international law also brought about a new stage in the development of soft law as a distinct category alongside the classical sources of international law. In this new context, soft law instruments proliferated and diversified significantly. This also led to a diversification of the functions soft law came to be used for.

With numerous international organisations adopting a vast number of resolutions and declarations etc. each year, it is easy to see how the establishment of international organisations significantly expanded the potential areas for international regulation. This expansion also made international legal practitioners realise that not all aspects of all of these areas could be regulated by formal international law-making. Here, soft law came to fulfil the role of a "gap-filling tool" that allowed for additional, more flexible arrangements alongside the classical treaty infrastructure. This ultimately resulted in soft law's proliferation across many different subject areas.

With international organisations' many governing and quasi-legislative bodies, a new type of soft law instrument entered the scene: secondary acts of international organisations. Their precise legal significance was (and sometimes still is) the subject of vigorous debate. Think, for example, of the discussions about the legal significance of General Assembly resolutions on the New International Economic Order in the 1970s and the varying opinions as to the degree to which these resolutions reflected customary international law. This is emblematic of a general diversification of soft law instruments, which has made it considerably more difficult to gauge their respective normativity and legal significance. The complexity of the issue was aptly described by Jorge Castañeda in his 1969 study of the legal effects of United Nations resolutions. He concluded at the time that the practice of international organisations was no less incongruous and inconsistent than a century ago, nor was the terminology more precise and uniform, and disagreements still persisted over questions as essential and basic as the compulsory or voluntary character of certain budgetary resolutions.

Finally, proliferation and diversification of soft law instruments was also accompanied by a corresponding diversification of the functions of soft law. In the context of soft law instruments replacing classical international treaties, the main virtue of such non-treaty instruments probably was (and still is) the increased flexibility in their adoption, which, for example, does not come with ratification requirements and the need for domestic parliamentary approval. In this context, soft law came to assume additional functions. For instance, it was increasingly seen as a way of tentatively capturing an initial understanding on an issue, paving the way for "harder" normative developments which might crystallise later, as was already highlighted in Castañeda's 1969 study of UN resolutions.

The proliferation and diversification of soft law instruments and their functions also show the severe limits of "soft law" as a term of analysis. Because of the significant differences that now exist between various informal instruments, using the term "soft law" runs the risk of treating instruments as the same, or at least as similar, while they are in fact quite different in terms of their origins, normative value and legal significance. This is part of the reason why Christine Chinkin has criticised the term "soft law" as a "misleading simplification". However, perhaps this is also precisely the appeal of the term.

Hybrid agreements as the new way forward?

This brings me to the third and most recent stage of development in the conceptual history of soft law, which is characterised by an even deeper integration of informal elements into the international legal order. Such elements increasingly make their entrance into formal legal instruments, as seen by the adoption of what could be called "hybrid agreements". These are legally-binding treaties in the sense of the Vienna Convention on the Law of Treaties (VCLT) that, despite their overall binding nature, contain a significant amount of non-binding provisions, thus creating a formally binding document of a normatively diluted legal character.

This is not a new phenomenon per se: there are earlier examples of treaties with provisions of a normatively vague and abstract nature. In recent years, however, there have been at least two prominent examples of major international treaties that arguably rely on these kinds of non-committal provisions to an extent previously unknown: the Paris Agreement of 2015 and the Pandemic Agreement of this year. What are the defining features of these two treaties? In a way, a lot stays the same: like other treaties, these agreements, too, are subject to ratification, and the general rules of interpretation in Articles 31-33 of the VCLT apply. However, they both exhibit a mixed legal structure and combine various hard, soft, and non-obligations. For instance, the Pandemic Agreement contains quite a few provisions, such as Article 15 on the whole-of-government and whole-of-society approaches to pandemic prevention, preparedness and response, that simply "encourage" and "urge" State parties to take action on key issues of pandemic governance. Many of the provisions are qualified by terms such as "as appropriate", relativising their otherwise concrete normative value. While not every use of such a term can be taken to dilute the respective provision, overall, it is questionable whether these kinds of provisions will provide a sufficiently concrete normative yardstick.

What conclusions can be drawn from these hybrid agreements for the history of soft law in international law? Today, informal elements can no longer be exclusively conceived as more or less clearly distinguishable, gap-filling complements to the international treaty infrastructure. Instead, they also increasingly permeate classical "hard law", resulting in a further blurring of the line between law and non-law. Of course, this is not to say that there were not good reasons for choosing this approach in both the Paris Agreement and the Pandemic Agreement. In setting up a comprehensive governance framework for problems as complex as climate change or pandemics, it might to a certain degree be unavoidable to combine traditional law-making elements with more flexible ones. However, there is a risk of soft law being used simply to obscure a lack of political consensus or willingness to act. Additionally, when soft law becomes ever more deeply embedded in the international legal order and the share of non-obligations becomes too high, this might also gradually put the entire legal order into jeopardy.

Conclusion

This short trip through the conceptual history of soft law has shown that informal instruments have gained a lot of traction over time. This can largely be explained by the need to account for the complexities of international governance that have come with increased institutionalisation on the international level and the expansion of international law across many different subject areas. Alongside this development, our understanding of what soft law means and to what end it might be utilised has equally evolved. Today, soft law arguably plays a much more prominent role than it has in the past, increasingly blurring the dividing lines between legally binding and non-legally binding instruments and between formal and informal mechanisms of governance. While soft law elements can indeed provide regulatory benefits and play a constructive role alongside formal instruments, revisiting these three steps in soft law's journey through the years has also demonstrated that soft law is not a panacea that comes without costs. Therefore, we should be mindful of both the strengths and shortcomings of soft law and reflect on its precise contours and effects in any given context. By adopting a nuanced understanding of soft law, we maintain the fundamental notion that there still is a (blurred) line between what is law and what is simply politics and can avoid providing an additional back door to those who want to retreat entirely from an international order governed by law.

Author:

Felix Schott, Doctoral Candidate and Research & Teaching Fellow at Freie Universität Berlin