Co-Head of the CIL OLP Team, Dr Tara Davenport, published a book chapter on “The use of submarine cable infrastructure for intelligence collection,” in Russell Buchan and Inaki Navarrete (eds), Research Handbook on Intelligence and International Law (Edward Elgar 2025). More details are available here.  

The chapter explored the international law applicable to the use of submarine cable infrastructure for intelligence collection either for underwater surveillance or the interception of data that is flowing through cable infrastructure. While there are no explicit rules governing the use of submarine cables for intelligence collection, this chapter explored several international legal frameworks that may govern this activity including the law of the sea, principles of territorial sovereignty, international telecommunications law, as well as human rights law (which may be implicated to the extent that data that is intercepted from submarine cables includes citizens’ private communications). The chapter concluded that determining the legality or permissibility of intelligence collection via cable infrastructure in each separate field of international law under discussion is not clear-cut and that it appears that this activity is not expressly prohibited by any of the fields of law under discussion – in other words, there is no clear and indisputable primary obligation to refrain from using cable infrastructure for intelligence collection. Nonetheless, the law of the sea and international human rights law provide some precedent for imposing limits on the use of cable infrastructure for intelligence collection in the form of the due regard obligation and peaceful purposes requirements (law of the sea) and some form of assessment of proportionality (human rights law) before undertaking intelligence collection via cable infrastructure. The chapter highlighted that further research and discussion is needed on establishing clear steps that states should take before utilising cables for intelligence collection as well as on mechanisms that will ensure that states are taking these steps. These calculations are particularly important when considering the importance of cable infrastructure to states and individuals alike.