In United States v. Jones, the U.S. Supreme Court considered whether gathering four weeks of GPS information capturing a suspect’s movement on public roads constituted an unlawful search under the Fourth Amendment of the U.S. Constitution.

In two separate concurring opinions, Justices Alito and Sotomayor rejected the notion that all of a citizen’s movements in public were free from the Amendment’s protection. A unifying theme for both justices was the power of contemporary technology to aggregate isolated acts into a comprehensive knowledge of a person’s private life. Justice Alito writing on behalf of four Justices notes that, over time, the collection of “a precise, comprehensive record of a person’s public movements reflects a wealth of detail about her familial, political, professional, religious, and sexual associations.” Separately, Justice Sotomayor writes that tracking technology provides “a substantial quantum of intimate information…that enables the Government to ascertain, more or less at will, [a person’s] political and religious beliefs, sexual habits, and so on.”

As in Jones, practices aggregating isolated acts into knowledge has typically focused on the impact on individuals. This Article inverts that focus. Just as aggregating isolated pieces of public information provides tremendous knowledge of individuals, it also provide tremendous knowledge as to the acts and beliefs of governments, the very elements that govern the formation of customary international law (CIL).

As it stands, the established mechanisms of international law formation have stalled. A primary cause of this legal sluggishness is the perceived illegitimacy of customary international law. The design of CIL, emergent from the civil law tradition, was intended to enable a dynamic body of legal norms untethered to text. Over time, both perceived and real infirmities within the system’s understanding of customary law have left customary law as a source of last resort.

“Networked custom” offers an alternative understanding of CIL formation to reinvigorate the intended dynamism of CIL by tracking it to distillations of society’s diverse and dispersed. While not embracing particular methodologies, the Article also explains the necessary characteristics and limiting principles in capturing networked intelligence. Ultimately, with a theoretical framework in place, this piece explains how applying networked custom can repair CIL’s legitimacy, restore its dynamism, and positively influence the unfolding expansion of international legal personality.


61 U. Kan. L. Rev. 659 (2013)


Customary international law, International law, Claims, Technology & law, Social norms

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