3.3.3. Private law

Both categories of sources of international law considered above, hard law and soft law, are sources of public international law. Private international law is traditionally considered something else entirely. In fact, some scholars take the view that it is a misnomer to call it international law at all, since the conflict of laws rules used to determine which state’s law should apply to an international dispute are domestic, and so are the laws that it is eventually decided should apply.[1]

Whilst this observation may be true, it implicitly limits the scope of international law to its traditional narrower sense of relations between states. If states are not the only international actors, and public law is not the only law, then private international law is indeed international law, and the private sector, not states, are its principal players.[2] This is particularly so when considering private international law not simply as a regime of conflict of laws, but as an independent and private source of governance which co-exists with (and may also be adopted into) national legal systems or hard international law, as for example in the case of the international commercial arbitration regime.[3]

Even in the narrower sense in which private international law is restricted to rules of conflict of laws, these rules can be seen as limitations on state sovereignty, in that they define the extent to which a state’s authority extends to private arrangements made in the transnational arena. This alone gives them the quintessential character of public international law.

Private international law in this narrower sense will fall for consideration later in the discussion of the jurisdictional limitations of international law,[4] whilst private law in the broader sense of transnational law will be discussed here. Transnational law

An outline of the content of transnational law—or at least, that subset of it found in the new law merchant—has been given at Section, but it has not been precisely defined. For present purposes, transnational law comprises those forms of international governance that exist apart from formal state or intergovernmental institutions, or as Rosenau puts it, “regulatory mechanisms in a sphere of activity which function effectively even though they are not endowed with formal authority.”[5]

It was foreshadowed above that we would here revisit the question of whether such law can be considered to be international law proper. In the absence of sufficient evidence of state practice and opinio juris to support its elevation into customary international law, the answer has to be that it cannot, in conventional terms. At most, individual rules or specific regimes may attain that status, but not the full corpus of transnational law.

But the very fact that we must consider the legal status of private law in terms of whether sufficient evidence of state practice has been amassed reveals the perversity of the exercise and how impoverished the conventional understanding of international law is. Twining writes,

A ius humanitatis, a transnational lex mercatoria, Islamic law, transnational humanitarian and human rights law, and, in a different way, some new regional orderings, and even parts of public international law itself are all arguably more or less clear examples of the amorphous category “non-state law.” ... [A]n account of the phenomenon of law in the contemporary world would for most purposes be incomplete if it did not treat of [these] legal families and legal cultures.[6]

Whilst one might demur at whether some of these examples do or should have the status of law, the criteria by which their claim to do so can be assessed should surely be capable of empirical assessment, rather than turning upon a formalistic Westphalian doctrine that only admits of laws made by or agreed between governments as law. So, what is law, fundamentally?

H L A Hart’s classic examination of this question in The Concept of Law concluded that a legal system is a system of primary and secondary rules—primary rules governing conduct that are generally obeyed by the citizens, and secondary rules governing how primary rules are made, amended, repealed, interpreted etc, that are accepted by public officials.[7] But Hart did not claim to offer a definitive definition of law,[8] and indeed he did not do so, as by his own concession his conclusions were problematic for international law which lacked many of the features of a fully developed legal system, yet was widely recognised as law.

A more recent attempt to accommodate diverse legal phenomena within a single framework is Tamanaha’s A General Jurisprudence of Law and Society, in which he reassesses Hart, abstracts out some of the conceptual underpinnings of his Concept of Law, and concludes simply that “Law is whatever people identify and treat through their social practices as law.”[9] If this sounds familiar, it may be the echo of the authority and control test of the New Haven School, or even the opinio juris test for the existence of customary international law, as all of these are to a large degree restatements of the same recurrent theme, expressed with greater or lesser generality.

On this basis, it can be concluded that whilst transnational law may not be international law as such, the formal defining criteria of international law are too narrow to be complete (or perhaps even useful) in the post-Westphalian age, as they leave a gaping hole between international law and domestic law, for which there is no conceptually consistent reason, and to which orthodox international lawyers are wilfully blind.

The concept of transnational law as law fills that hole, allowing non-state actors and their private law the conceptual place in international society that they already, plainly, possess in fact. This is even beginning to be recognised within the United Nations. As Fernando Cardoso, Chair of the High Level Panel on UN–Civil Society, commented in 2003:

This on-going process of building a cosmopolitan law represented a great leap towards a world order that is not based on the uncontested will of sovereign states, but on universally agreed principles and norms. In a major break with the past, individuals were acknowledged as subjects not only of national law, but also of cosmopolitan rules, enforceable by transnational institutions.[10]

The relevance of this conclusion is that it greatly broadens the potential lawmaking role of the IGF, since it is primarily transnational law, and only incidentally (if at all) international law, that is the product of public policy governance by network.[11]



Nygh, P E, Conflict of Laws in Australia (1995), 4


See Cutler, A C, Private Power and Global Authority: Transnational Merchant Law in the Global Political Economy (2003), 32–54; Janis, Mark W, Why Do We Continue to Distinguish Between Public and Private International Law? (1985)


Cutler, A C, Private Power and Global Authority: Transnational Merchant Law in the Global Political Economy (2003), 40


See Section 3.4.2.


Rosenau, James N, Governance, Order and Change in World Politics (1992), 5


Twining, William, Globalisation and Legal Theory (2000), 52


Hart, H L A, The Concept of Law (1987), 116


Hart, H L A, The Concept of Law (1987), 213


Tamanaha, Brian Z, A General Jurisprudence of Law and Society (2001), 194


Cardoso, Fernando H, Civil Society and Global Governance (2003), 3


Even so, to avoid confusion this will be described in future chapters as a “policy-setting” rather than a “lawmaking” role: see Section 6.2.