It was in the context of codification that struggle over the internationalisation of protection against rebels played out in its most explicit confrontation, culminating in the League of Nations’ Codification Conference held at The Hague in 1930. If the rules coming out of the arbitral practice rested on shaky and contested authority, and were inextricably tied up with practices of intervention, formal multilateral codification offered Latin American international lawyers a means to set clear and mutually agreed standards that would restrict occasions for intervention. At the same time, Anglo-American international lawyers sought to codify responsibility on their own terms. This was codification as the technical practice of elite lawyers, simply a continuation of arbitration and scholarship – a surreptitious means to universalise US ways of doing things. The attempt to reconcile the two contrasting approaches to codification and responsibility ended in stalemate at The Hague.

In the nineteenth- and early-twentieth centuries, mixed claims commissions were established as a way of resolving claims for injuries caused to foreign nationals by rebels when political instability, especially in the form of revolution and civil war, threatened foreign imperial and commercial ambitions and interrupted periods of capitalist expansion in decolonised Mexico and Venezuela. Enforcing state responsibility for such claims was often the justification for intervention in Latin America during the late nineteenth- and early twentieth-centuries. While not all of the mixed claims commissions were imposed by the threat or use of force, invasion, occupation and bombardment existed alongside arbitration as part of a spectrum of more or less coercive measures to protect foreign commerce and capital during this time. The system of mixed claims commissions – as a political intervention in decolonised Latin America – served to insulate global economic liberalisation against revolution and civil war in the decolonised world, by taking the question of who assumed the risk of harm by rebels out of the scope of national authority.

The idea that states have to exercise due diligence in protecting investments against non-state armed actors and Article 10 of the Articles on the Responsibility of States for Internationally Wrongful Acts have common origins in the emergence and contestation of the rules of state responsibility for injuries to foreign nationals (or ‘aliens’) by rebels during the nineteenth- and early-twentieth centuries. Tracing these common origins, the story starts with a series of arbitrations involving Latin American states that were set up between 1839 and 1927. It then follows the scholarly debates about state responsibility for rebels that proliferated particularly from the turn of the twentieth century onwards, finishing with the League of Nations Codification Conference at The Hague in 1930 where states failed to agree a convention on responsibility. This first chapter sets out the book’s main argument and situates it theoretically and methodologically.

With the failure to codify, state responsibility for rebels went quiet. After the 1930s, there were no more of the great suites of mixed claims commissions. Scholarship on the topic dried up. Nevertheless, we can follow the trajectory of state responsibility for injuries to aliens by rebels as it split in two. On one hand, we have the International Law Commission (ILC)’s half-century odyssey to codify state responsibility, and on the other, the emergence of international investment law. The story of state responsibility for rebels and its legacy for both the modern law of state responsibility and international investment law have a number of implications for international law scholars and practitioners today: for specific legal issues in the law of state responsibility and international investment law, for our understanding of the development of these fields and for the state of the law today when it comes to responsibility for the acts of armed groups across various fields including international human rights and humanitarian law. Finally, it allows us to put together these fragments of state responsibility for rebels and tells us something about the whole, exposing how today international law prioritises the protection of foreign investment against rebels, and non-state armed actors more generally, in the decolonised world.

The mixed claims commissions, which had a degree of autonomy from the agendas of the states that imposed them, produced a rich and extensive body of case law on state responsibility for rebels. The practice of the commissions to enforce claims based in contract greatly increased the scope of state responsibility for rebels, in a way that reduced the risks for foreign nationals of doing business in Latin America and insulated commercial relations from political instability; the arbitral practice had a politics, even if it did not necessarily or straightforwardly reflect the context of the commissions’ establishment. The commissions engaged with a number of important international legal rules and principles: the general principle of non-responsibility for rebels, with exceptions for successful rebels, rebels who establish de facto authority and negligence in failing to protect against rebels. The exceptions to non-responsibility, particularly the duty of protection, would end up being more important than the rule. At the same time, the practice of the commissions was at times contradictory and ambiguous, providing only the shakiest foundation for future obligations.

The first moves to develop rules of state responsibility for rebels were made by Latin American international lawyers who sought to resist intervention on the basis of enforcing revolutionary damage claims. Later, Anglo-American international lawyers sought to reconcile rules from the arbitral practice, rules that often justified intervention and reinforced the legal impact of intervention. This was something that took a lot of interpretive work given how inconsistent and unstable the practice was. This dynamic of resistance and development – a battle over the meaning and authority of the arbitral practice – drove the emergence of state responsibility for rebels as a flourishing, if disputed, sub-field of international law.While nearly all the various positions made responsibility for rebels the exception rather than the rule, Latin American international lawyers tended towards narrow exceptions defined by reference to national treatment. Anglo-Americans, in contrast, based expansive exceptions on an international standard of alien protection. These debates can be understood as a struggle over the internationalisation of protection against rebels, structured around questions of whether the standard of protection against rebels owed by states to aliens was nationally or internationally determined and whether it was domestic or international authority that adjudicated such standard.