4.1 Summary of Principal Findings
This thesis has examined a specific but increasingly consequential normative gap in international law: the absence of any established framework for the environmental impact assessment of space object reentries in areas beyond national jurisdiction. The central argument is that this gap has been substantially addressed, though not fully resolved, by the entry into force of the BBNJ in January 2026. The thesis’s findings against each of its four research questions are as follows.
On the first research question, what environmental harm is caused by space object reentries and splashdowns, and to what extent is it legally recognized, the thesis finds that the harm is real, multidimensional, and legally significant, as demonstrated in Parts 1 and 2, yet systematically unrecognised under the existing regulatory frameworks.(1) Muñoz-Patchen, “Regulating the Space Commons,” 233–59. International space law has not recognised these impacts as legally relevant; UNCLOS and the BBNJ, through their broad “any source” and “any source of pollution” language, are capable of doing so. The first contribution of this thesis is to bring this empirical reality into contact with the applicable legal frameworks and to demonstrate that the environmental harm is within the scope of existing treaty obligations.
On the second research question, what obligations launching States bear under the OST, customary international law, and UNCLOS, the thesis finds that those obligations are broader than existing practice acknowledges. The OST’s launching State framework, read in conjunction with Article VI’s responsibility for national activities and Article IX’s due regard standard, generates a general obligation of diligent oversight over the entire lifecycle of a space object, including its end-of-life disposal. UNCLOS Articles 192, 194, and 206 impose independently binding obligations to protect the marine environment and to conduct EIAs before authorising activities likely to cause significant marine harm. Customary international law, as affirmed in Pulp Mills (ICJ, 2010) and confirmed in the ITLOS Climate Change Advisory Opinion (2024), requires EIAs as a component of the general due diligence standard for activities with the potential for significant harm to shared or transboundary environments. These obligations apply cumulatively and are not diminished by the absence of a specific space-marine interface norm; on the contrary, the very absence of such a norm within the space law framework means that the marine law framework fills the gap.
On the third research question, to what extent the BBNJ’s EIA obligation applies to splashdown operations and how compliance differs from previous practice, the thesis finds that the BBNJ applies fully to controlled splashdowns as “planned activities” under Part IV, and with high probability to deliberate deorbit manoeuvres even where the final impact point is uncertain. The BBNJ’s Article 5 “not undermine” clause does not exempt splashdowns from the EIA framework because: (a) the EIA obligation pre-exists the BBNJ and is grounded in UNCLOS Article 206 and customary law; (b) space law does not address marine environmental impacts and therefore does not constitute a competing framework in the relevant domain; and (c) space activities were not included among the sector-specific carve-outs, a fact that, while consistent with the BBNJ’s general applicability to marine-impacting activities in ABNJ, does not by itself constitute definitive negotiating history and is best understood as a secondary argument that reinforces the primary object-and-purpose analysis. Compliance with the BBNJ framework represents a transformative departure from previous practice: pre-authorisation screening, marine baseline assessments, cumulative impact analysis, public reporting to the Scientific and Technical Body, and post-activity monitoring are all obligations that no spacefaring State has historically applied to splashdown authorisations.
On the fourth research question, whether current splashdown practice is consistent with binding international environmental law, the thesis’s answer is unequivocal: it is not. No launching State has conducted a pre-authorisation EIA of a splashdown’s marine environmental impacts. No State has assessed the cumulative environmental burden at the spacecraft cemetery. No post-activity monitoring programme exists for any historical splashdown site. The compliance gap is not marginal; it is structural and systemic. The BBNJ’s entry into force has converted what might previously have been characterised as a soft obligation into a binding procedural requirement for all State Parties. For spacefaring States that are Parties to the BBNJ, authorising a splashdown without a prior marine EIA now constitutes a breach of their treaty obligations.