MarIus

2.2.1 The EIA Obligation Pre-Exists the BBNJ

The first ground for rejecting the displacement argument is structural. Article 5(2) requires the BBNJ to be interpreted and applied in a manner that does not undermine relevant instruments and frameworks. But the core obligation to conduct an EIA is contained in Article 206 of UNCLOS itself, not in the BBNJ.(9) UNCLOS, art. 206. The BBNJ operationalises and procedurally elaborates an obligation that is already binding under UNCLOS as treaty law, and independently under customary international law as affirmed by the International Court of Justice in Pulp Mills on the River Uruguay.^{(10) Pulp Mills, I.C.J. Reports 2010.}

The "not undermine" clause cannot be read to override a pre-existing UNCLOS obligation; such a reading would have the implementing agreement subordinate the parent Convention, which is neither grammatically nor structurally coherent. The clause addresses the BBNJ’s relationship with other bodies and instruments, not its relationship with UNCLOS itself. The BBNJ is concluded under UNCLOS, and its provisions are to be interpreted in light of UNCLOS, not as derogating from it. Invoking Article 5 to displace UNCLOS Article 206 would invert the implementing-agreement/parent-Convention hierarchy; the BBNJ was adopted to operationalise that very obligation, and its relationship clause cannot be read to diminish it.

2.2.2 Space Law Does Not Address Marine Environmental Impacts

The second ground is substantive: the OST and the associated UNCOPUOS guidelines do not address the marine environmental consequences of splashdowns at all. They regulate the space environment the sustainability of orbital use, the mitigation of collision risk, and the liability framework for surface damage to persons and property.(11) Outer Space Treaty, art. VII, Space Debris Mitigation Guidelines (2021) and Liability Convention. The OST framework was designed for an era in which the primary concerns were the weaponisation of space, the appropriation of celestial bodies, and the attribution of liability for objects falling from orbit.(12) Frans von der Dunk, ed., National Space Legislation in Europe: Issues of Authorisation of Private Space Activities in the Light of Developments in European Space Cooperation, vol. 6, Studies in Space Law(Leiden: Nijhoff, 2011), 3–28. The marine ecosystem of the high seas was not among the values the OST was designed to protect, and no subsequent space law instrument has addressed that gap.

Recent research has helped advance understanding as to what the gap means in practice. Reentry survivability analysis indicates that metallic components — aluminium alloys, stainless steel, and titanium — routinely survive ablation and reach the ocean surface intact.(13) Shareefdeen and Al-Najjar, “Pollution Effects,” 5127–41. The use of highly toxic propellants such as hydrazine in launch vehicles raises concerns about marine environmental harm upon reentry and splashdown, yet existing research on the marine environmental effects of spaceflights remains piecemeal, and the risks and extent of environmental degradation from accelerating splashdown operations are subject to significant scientific uncertainty.(14) Alla Pozdnakova, "Pollution of the Marine Environment by Spaceflights," in The Environmental Rule of Law for Oceans, ed. Froukje Maria Platjouw and Alla Pozdnakova (Cambridge: Cambridge University Press, 2023), chap. 10. The spacecraft cemetery at Point Nemo is not an ecological void: the area supports marine life including abyssal fauna and microbial communities, and the ocean floor likely hosts a multiplicity of vulnerable ecosystems.(15) Vito De Lucia and Viviana Iavicoli, "From Outer Space to Ocean Depths: The ‘Spacecraft Cemetery’ and the Protection of the Marine Environment in Areas beyond National Jurisdiction," California Western International Law Journal 49, no. 2 (2018): 368–70. Yet international space law is entirely silent on any duty to conduct an environmental impact assessment before authorising a splashdown. COPUOS holds no marine environmental law-making mandate, and the resulting framework remains fragmented and insufficient to address the marine environmental consequences of spaceflights, a gap that arguably calls for resolution through a global instrument on biodiversity in areas beyond national jurisdiction.(16) Pozdnakova, "Pollution of the Marine Environment by Spaceflights," 81, 84, 91–92.

The BBNJ attempts to reconcile contrasting views by providing that it promotes coherence and coordination with existing bodies but does not undermine them.(17) BBNJ, art. 5(2); De Lucia and Iavicoli, "From Outer Space to Ocean Depths." In the present context, however, "coherence and coordination" with the space law regime means treating it as the applicable law for the orbital phase of a space object's life, and the BBNJ and UNCLOS as applicable for the end-of-life oceanic phase. These are sequential, not competing, regulatory domains. There is no conflict to resolve because the two regimes do not purport to govern the same thing. The structural point can be put more precisely: Article 5 protects existing frameworks from being undermined — but only where those frameworks actually regulate the matter in question. Space law's complete silence on marine environmental impacts means there is no applicable framework to protect in the relevant domain. The BBNJ does not displace the space law regime; it fills a genuine regulatory vacuum that the space law regime has never occupied.

This characterisation rests on object-and-purpose interpretation under VCLT Article 31 rather than on inferences from drafting silence alone. Where a specialised body lacks competence over the subject matter in question, such as marine environmental impact assessments, the general framework with that competence applies.(18)Responsibilities and Obligations of States with Respect to Activities in the Area, Advisory Opinion, ITLOS Case No. 17 (February 1, 2011), para. 148. UNCOPUOS has no marine environmental mandate and has never purported to exercise one; it cannot therefore constitute the "relevant global body" within the meaning of Article 5 for purposes of assessing marine impacts of splashdown operations.(19) UNCOPUOS, Space Debris Mitigation Guidelines, UN Doc. A/62/20, annex; BBNJ, art. 5(2).

2.2.3 The Significance of the Absence of a Space Activities Carve-Out

Article 29 of the BBNJ permits States to satisfy their EIA obligations through assessments conducted under other relevant instruments, provided those assessments meet an equivalency standard.(20) BBNJ, art. 29. Space activities benefit from no sector-specific carve-out analogous to those available for high seas fisheries, shipping, or seabed mining, an absence which is legally significant. Furthermore, Article 5 does not clearly exclude space activities from the BBNJ framework and, read in conjunction with UNCLOS Article 206 and the customary EIA obligation, the BBNJ applies to planned splashdowns in ABNJ that may cause significant adverse marine environmental impacts.(21)Vienna Convention on the Law of Treaties, art. 31; De Lucia, "Rethinking the Conservation of Marine Biodiversity," 3–4.

Article 5 does not operate as a blanket exclusion of activities regulated elsewhere. Read together with Article 29(3), it establishes not only a defensive constraint, the BBNJ framework must not undermine existing sectoral regimes, but a positive obligation to promote coherence between BBNJ EIA standards and those of other relevant bodies.(22) BBNJ, arts. 5(2), 29(3) States Parties who are also members of UNCOPUOS are accordingly under an obligation to advocate within that body for space-specific EIA guidelines compatible with BBNJ standards. The "not undermine" clause is therefore better understood as a floor, not a ceiling, of the BBNJ’s engagement with existing frameworks.(23) Friedman and Blasiak, "Beyond 'Not Undermining,'" 453–54; De Lucia, "Rethinking the Conservation of Marine Biodiversity," 3–4.

A final objection concerns State practice. Oceanic splashdowns are routinely authorised without marine EIA. NASA's ISS Transition Report, the primary planning document for the largest splashdown in history, targets Point Nemo without reference to any high seas assessment obligation under applicable marine frameworks;(24) National Aeronautics and Space Administration, International Space Station Transition Report, January 2022, https://www.nasa.gov/wp-content/uploads/2015/01/2022_iss_transition_report final_tag-ged.pdf.; De Lucia, "Splashing Down the ISS," para. 5. ESA's Zero Debris Charter endorses controlled ocean disposal as responsible end-of-life practice without engaging the BBNJ framework;(25) ESA, "Zero Debris Charter." and commercial operators proceed without assessment of marine environmental impacts.(26) De Lucia and Guo, "Assessing before Sinking," 1–29. This practice does not, however, generate permissive counter-custom, for two reasons. First, all such practice predates the BBNJ’s entry into force on 17 January 2026; pre-entry-into-force conduct cannot negate obligations that did not yet exist, and the pre-existing customary obligation under UNCLOS Article 206 was equally not discharged by that practice.(27)Vienna Convention on the Law of Treaties, art. 18; UNCLOS, art. 206; Second, the obligations at issue are in part erga omnes obligations under UNCLOS Part XII and not susceptible to derogation through consistent unilateral State practice.(28) ILC, Responsibility of States, art. 48(1)(b); UNCLOS, arts. 192, 194. The compliance gap evidenced by current State conduct is therefore a finding about implementation, not about the existence of the legal obligation.

2.2.4 Rebutting Practice-Based Defences

The legacy practice argument, that decades of consistent State practice targeting the high seas for controlled reentry demonstrates acquiescence in the absence of any EIA obligation is, in the author’s opinion, unpersuasive. The practice predates the BBNJ's entry into force and cannot negate treaty obligations that did not yet exist. More fundamentally, the EIA obligation does not originate in the BBNJ: it follows from the duty of due diligence as a matter of general international environmental law and is a necessary corollary of the principle of prevention under UNCLOS Article 206.(29) UNCLOS, art. 206; Pozdnakova, "Pollution of the Marine Environment by Spaceflights," 88–90. Legacy practice accordingly failed to discharge a pre-existing binding obligation; and the absence of a consistent and uniform international approach to EIA for spaceflight activities does not establish acquiescence in the absence of obligation, it reflects, rather, a pattern of underutilization of existing legal requirements that may itself constitute infringement of the due diligence standard.(30) Pozdnakova, "Pollution of the Marine Environment by Spaceflights," 90

A second argument may purport that the voluntary guidelines set forth by the IADC Space Debris Mitigation Guidelines and the ESA Zero Debris Charter provide an adequate environmental framework, rendering BBNJ EIA compliance unnecessary. However, voluntary technical guidelines cannot substitute for binding due diligence obligations confirmed by international tribunals.(31) ILC, Responsibility of States, Further, neither instrument contains any provision for marine EIA, public notification, or scientific review — the minimum procedural content required for equivalency under the BBNJ.(32) BBNJ, art. 29(4)(b).

A third argument may claim that the ISS 2030 deorbit represents an early application of a still-forming governance framework and should not be assessed against fully crystallised legal obligations. This “nascent regime” argument has limited temporal force but cannot excuse prospective non-compliance. The BBNJ is in force and its EIA obligations bind States Parties; the ISS deorbit is a planned future activity, precisely the category of conduct to which Article 28(1) applies, and its operational timeline provides both the lead time and institutional capacity to render compliance entirely feasible.(33) BBNJ, art. 29(4)(b); Inter-Agency Space Debris Coordination Committee, IADC Space Debris Mitigation Guidelines, IADC-02-01 (rev. 2021);