The Liability Convention, 1972, lays down two different legal regimes for damages caused by space objects “on the surface of the earth or to aircraft flight” (Art. II) or occurring “elsewhere than on the surface of the earth to a space object […] or to persons or property on board” (Art. III). Respectively, the State shall be “absolutely liable”, or “liable only due to its fault or the fault of persons for whom it is responsible”. Absolute liability is usually justified by the high risk inherent in space activities and requires only proof of the causal relationship between the event and the damages, regardless of the violation of a specific norm of due diligence, which is instead the basis of fault liability.

In a context of increasing orbit congestion and resultant high risk of collisions in space, the topic of fault liability deserves further definition. The specific parameters to determine the degree of fault especially remain to be properly identified. Acts of hard international law such as the Liability Convention leave the matter unaddressed, and the academic discussion has slowly progressed over the years. 

Nevertheless, there is a concrete opportunity to refer to soft law norms – such as the ones contained in the 2019 COPUOS Guidelines for the Long-term Sustainability of Outer Space Activities as well as future STM rules potentially adopted – to build up specific criteria to measure the diligence maintained by a State while conducting space activities. If those rules served as the basis for parameters to assess the degree of fault, then this framework would result in a win-win situation: first, soft law acts will be used as points of reference in judicial and ADR cases, and consequently their implementation worldwide will be enhanced. Soft law guidelines and best practices may therefore aim at becoming the customary standard of care in conducting space activities, so gradually acquiring binding force.

Finally, the technical applicability of the agreed discipline would be under question. Actually and for instance, the large amount of SSA data that is currently available could be used as evidence of compliance with some of the established rules, despite the international challenges that could arise in agreeing on such a control mechanism.

On the whole, a clear identification of the parameters to measure fault would benefit the liability discipline, making it truly implementable, and in parallel could contribute to facilitating the establishment of incentivised and verifiable standards.