MarIus

2.4.1 The OST Launching State Framework

Under the OST, States bear international responsibility for national activities in outer space, whether conducted by governmental agencies or non-governmental entities. Article VI imposes two distinct prospective obligations: a requirement of prior authorisation of non-governmental activities, and an obligation of continuing supervision.(5) Stephan Hobe, Bernhard Schmidt-Tedd, and Kai-Uwe Schrogl, eds., Cologne Commentary on Space Law, vol. 1 (Cologne: Carl Heymanns Verlag, 2009), commentary on art. VI. These are distinct from the post-harm liability regime established by Article VII OST and elaborated by the Liability Convention, which distinguishes absolute liability for surface damage from fault-based liability for space damage and operates as a compensation mechanism triggered only upon the occurrence of harm.(6) Carl Q. Christol, The Modern International Law of Outer Space(New York: Pergamon Press, 1982), 195–218. The argument advanced in this thesis is grounded in Article VI, not Article VII: it is the preventive supervisory obligation, read in conjunction with UNCLOS Article 206 and the customary EIA duty, that requires States to assess marine environmental impacts before authorising a splashdown, irrespective of whether damage subsequently occurs and the liability regime is engaged.

A critical distinction must be drawn between State liability and State responsibility. The Liability Convention creates a secondary obligation to compensate upon the occurrence of damage; it imposes no positive obligation to prevent environmental harm or to conduct EIAs in advance. The obligations at issue in this thesis; BBNJ Article 6, UNCLOS Articles 192, 194, and 206, and the customary due diligence duty; are primary norms whose breach generates State responsibility under the framework codified in the ILC Articles on State Responsibility.(7) ILC, Responsibility of States, art. 4; Crawford, Peel, and Olleson, "The ILC's Articles," 975. Under that framework, a State incurs international responsibility where conduct attributable to it constitutes a breach of an international obligation.(8) Ibid. The launch licensing decision satisfies both elements: it is attributable to the authorising State under Article VI OST, and the substantive primary norm is supplied by the BBNJ and UNCLOS.(9) Outer Space Treaty, art. VI; BBNJ, arts. 6, 28(1).

Article VI is the functional equivalent of the due diligence standard under international environmental law: both impose a standard of conduct rather than of result; both require active oversight rather than passive licence-issuance; and both contemplate an ongoing supervisory role for the State over activities it has authorised.(10) Handl, "State Liability for Accidental Transnational Environmental Damage by Private Persons," 525–65, at 527; Pozdnakova, "Pollution of the Marine Environment by Spaceflights," 88–90. The obligation of "continuing supervision" under Article VI accordingly extends across the full lifecycle of a space object, including the deorbit decision and the selection of a splashdown zone; it does not lapse at atmospheric entry.

Crucially, Article VI requires States to assure that national activities are carried out in conformity with the Treaty, while Article III OST requires that space activities be conducted in accordance with international law generally.(11) Outer Space Treaty, arts. III, VI; The authorising State's responsibility under Article VI therefore encompasses compliance with applicable international environmental law, including the EIA duty under UNCLOS Article 206 and the customary due diligence obligation. A failure to conduct a marine EIA before authorising a controlled splashdown constitutes a breach of those primary obligations attributable to the authorising State, engaging State responsibility under the general framework.(12) Birnie, Boyle, and Redgwell, International Law and the Environment, 3rd ed., 137–42. This confirms that the authorising State exercises "jurisdiction or control" over a controlled splashdown within the meaning of BBNJ Articles 6 and 28(1).

The analysis in this section establishes three convergent propositions. First, the relevant obligations in the splashdown context are primary norms; the supervisory duty under Article VI OST, the environmental protection obligations under UNCLOS Part XII, and the EIA obligation under the BBNJ, whose breach engages State responsibility under the general international law framework; the Liability Convention's post-harm compensation regime is distinct and operates on a different legal plane.(13) Brownlie, System of the Law of Nations: State Responsibility, Part I, 44–51; Christol, The Modern International Law of Outer Space, 195–218. Second, the State bearing OST supervisory responsibility for a commercial splashdown is, in virtually all foreseeable cases, the same State bearing BBNJ EIA obligations for that operation: the act of authorisation that creates the Article VI nexus simultaneously constitutes the exercise of "jurisdiction or control" within the meaning of BBNJ Article 28(1).(14) Outer Space Treaty, arts. VI, VIII; Registration Convention, art. II. Third, the structural parallel between Article VI OST's "continuing supervision" standard and the due diligence obligation under international environmental law confirms that these frameworks are mutually reinforcing rather than in tension;(15) Pozdnakova, "Pollution of the Marine Environment by Spaceflights," 88–90; compliance with Article VI requires compliance with applicable environmental law, including the EIA duty, and a failure to discharge that duty constitutes a breach of a primary norm attributable to the authorising State under the ILC Articles on State Responsibility.(16) Outer Space Treaty, arts. III, VI; International Law Commission, Responsibility of States for Internationally Wrongful Acts, art. 12; Crawford, Peel, and Olleson,

2.4.2 The BBNJ's 'Jurisdiction or Control' Framework

Article 6 of the BBNJ imposes a general obligation on each Party to ensure that activities under its jurisdiction or control are conducted in a manner that prevents, reduces and controls significant adverse impacts on marine biological diversity in ABNJ. The EIA obligation in Part IV is one specific expression of this general obligation. Furthermore, Article 28(1) requires States to conduct EIAs for planned activities under their jurisdiction or control. The phrase 'jurisdiction or control' is broader than the OST's 'launching State' category, it covers activities conducted by commercial entities or private actors licensed or authorised by the State, as well as activities conducted by the State itself.

The ITLOS Seabed Mining Advisory Opinion confirms that the obligation of due diligence, a main component of the BBNJ’s EIA requirements, attaches to States by virtue of their having jurisdiction or control over an activity, regardless of whether the immediate actor is a State or a non-governmental entity.(17) V. Roeben and J. Guo, "The Result-Oriented Due Diligence Obligation in the ITLOS Climate Change Advisory Opinion: Developments and Implications," Review of European, Comparative and International Environmental Law(2026): 1–10, https://doi.org/10.1111/reel.70041. A State that licenses a commercial launch operator approves that operator's debris mitigation plan, and issues a licence authorising a controlled splashdown onto the high seas exercises 'jurisdiction or control' over that activity within the meaning of Article 6 and Article 28(1) of the BBNJ.

Article 6 therefore constitutes more than a jurisdictional allocation: it is the BBNJ’s primary substantive obligation. A State that conducts a technically compliant EIA but authorises an activity predictably causing significant adverse impacts may nonetheless be in breach of Article 6, since the obligation is to “ensure that activities… do not cause” significant adverse impacts, not merely to assess whether they might.(18) Crawford, Peel, and Olleson, "The ILC’s Articles," 963. European Journal of International Law12, no. 5 (2001): 963–91, https://doi.org/10.1093/ejil/12.5.963. The EIA is the procedural mechanism through which the Article 6 duty is discharged, but Article 6 provides the substantive benchmark against which the authorisation decision itself is measured.

2.4.3 Reconciling the Two Frameworks

The launching State under the OST and the State exercising jurisdiction or control under the BBNJ will, in most regulated commercial launch scenarios, be the same State. The State that registers the space object is typically also the State that licenses the launch and thereby exercises jurisdiction or control over the entire mission, including the terminal splashdown phase. When these categories overlap there is no attribution conflict: the same State bears OST responsibility for the orbital phase and BBNJ EIA obligations for the oceanic phase.(19) Outer Space Treaty, arts. VI, VIII; BBNJ, arts. 6, 28(1);

A mission lifecycle analysis illustrates the point. The orbital phase falls entirely within the OST framework and the space debris mitigation regime. The deorbit burn is the moment at which the BBNJ obligation crystallises: it is the act of authorising the descent, knowing the high seas is the intended endpoint, that triggers Articles 28(1) and 28(2). The atmospheric transit phase is a mixed domain in which OST jurisdiction over the registered object persists alongside aviation safety obligations. The ocean impact phase falls squarely within UNCLOS Part XII and BBNJ Part IV, since the space object has entered the marine environment in ABNJ.(20) UNCLOS, arts. 192, 194, 206; BBNJ, arts. 22–35. This analysis does not create a hierarchy between the instruments; it demonstrates that each governs the phase to which it applies, with the BBNJ capturing both the authorisation decision and the marine impact phase that the space law regime has never addressed. Where they diverge, for example, where a space object is launched from one State's territory under another State's license, or where a multi-State joint venture is involved, the analysis must proceed by identifying which State exercises effective jurisdiction or control over the splashdown decision. The BBNJ does not require a single responsible State; it requires that the Party (or Parties) with jurisdiction or control discharge the EIA obligation. In practice, this will be determined by the licensing and authorisation structure of the relevant national space law, which in most major spacefaring nations tracks the launching State concept closely.(21) Bennett, “Orbital Debris Requires Prevention and Mitigation across the Satellite Life Cycle,” 95.

The OST responsibility framework therefore functions as a useful interpretive guide for identifying the State bearing jurisdiction or control under BBNJ Article 6 but does not exhaust that category. A State may exercise 'control' over a splashdown operation even without being the formal launching State, for example, where it has issued a landing license, coordinated with coastal States regarding the splashdown zone, or otherwise assumed operational responsibility for the terminal phase of the mission.(22) Christian Villanueva, "State Governance for an Emerging Space Nation," SSRN Scholarly Paper No. 6217658 (Social Science Research Network, February 11, 2026), https://doi.org/10.2139/ssrn.6217658. The BBNJ's design ensures that no State can disclaim EIA obligations by reference to another State's formal registration of the space object.

2.4.4 Implications for Non-State Commercial Operators

The growth of private commercial spaceflight raises a specific attribution question. Under the OST, non-governmental entities may conduct space activities, but their activities are treated as 'national activities' for which the authorizing State bears international responsibility.^{(23) Yutaka Osada, "Governance of Space Resources Activities: In the Wake of the Artemis Accords," Georgetown Journal of International Law53 (2022), https://www.law.georgetown.edu/international-law-journal/wp-content/uploads/sites/21/2023/03/GT-GJIL230011.pdf.} A commercial launch operator, such as a private company holding a national launch license, is not itself a Party to the BBNJ. The BBNJ's EIA obligation falls on the Party that authorizes the activity, not on the operator directly.

The practical implication is that States with active commercial space industries must ensure that their national licensing and authorization frameworks require applicants to conduct (or demonstrate compliance with) EIA obligations for planned high-seas splashdowns before a license is issued. The EIA obligation thus functions as a domestic regulatory requirement that the State must discharge on the international plane, and which it may implement through its national space licensing regime. This creates an important role for national space law as a transmission mechanism between the BBNJ's international obligations and the commercial operators who are the immediate actors.