For much of recorded history, the individual had no standing in the international legal arena. They were considered to be citizens, and under the exclusive control, of the States. The leading modern case establishing the limits of private individuals in international law is the Danzig Railway Officials case. (Jurisdiction of the Courts of Danzig, PCIJ, Advisory Opinion (1928)). The opinion states, in part, that international agreements cannot create direct rights and obligations for individuals, but that the these agreements may provide for definite rules creating individual rights and obligations enforceable by the national courts of the signatory.
In the post World War II era, however, the individual has accrued rights and incurred responsibilities in international law, particularly in the area of human rights law. The rules of conflict, such ans the Geneva and Hague Conventions, as well as prohibitions against crimes against humanity, genocide, torture and terrorism, extend to both nation States and individuals. The Nuremburg Trials pierced the historical defense of the individual as a state actor, and extended international law to the individual.
Additionally, individuals are beginning to be able to exercise legal rights against states in the international legal arena. With the advent of effective international organization, courts, and treaties on human rights, individuals have gained the ability to petition international organizations and courts for a redress of grievances and enforcement of actions consistent with the power ceded to the international organizations by the member States. While the remedies are limited in both scope and effectiveness, the ability of the petitioner to invoke international tribunals and law where previously their only course for redress was to what could be hostile State courts represents a dramatic and underappreciated shift in international law.
The trend continues toward the protections and enhancement of human rights and liberties through the international justice system. While the ability to enforce is limited and generally set by treaty, the fact that millennia of legal precedent is collapsing in favor of individual human rights over States rights must not be overlooked. While this trend is often bemoaned in the United States as a spread of Federalism over State sovereignty, this trend is a global one, and represents the emergence of a new locus of governance at the individual with a focus on individual rights and duties.