The manuscript is clear and well structured. The existing international legal framework is exhaustively and precisely presented and analyzed. This manuscript will undoubtedly serve as a reference on the state of public international law in this field, and on the questions still outstanding. However, the manuscript could go even further, on the one hand, by precisely defining OAE and the possible differences between OAE as a CDR and OAE as a method of mitigating ocean acidification (e.g.: in practice, exists a difference between the two methods or the difference is only a difference of intention? ) and secondly, by comparing geoengineering techniques applicable to the oceans to answer two additional questions: do the specificities of climate geoengineering require the creation of a specific legal framework? If not, how can we involve all the institutional players concerned in legal discussions on the framework for geoengineering (creation of a committee?)?

Overall, this is an excellent chapter which provides an up-to date, well-structured and balanced assessment of legal considerations relevant to research of OAE. That said, taking into account that the authors focus on OAE research and argue that research and (commercial) deployment should be treated differently under international law, I would encourage the authors to include some further analysis on how to distinguish the two categories of activities concerned (what is the relevance of the LP assessment framework here?). Furthermore, I would recommend that the authors address the following minor issues before the manuscript is accepted for publication:

Line 29: The term 'common pool resource' requires clarification. Usage of this term is perhaps also not completely accurate in light of the different regimes of the various maritime zones under the international law of the sea.

Line 35: I recommend to include a clarification that States are bound to CIL unless they have persistently objected to the rule/principle concerned. In the context of OAE research, this may be relevant with regard to the precuationary principle/approach.

Line 115 (table 1): It is subject for debate whether Part VII of UNCLOS really only applies to the 'water column'. I would arge that the regime of the high seas also applies to the seabed and subsoil beyond the outer limits of the continental shelf unless Part XI of UNCLOS contains leges speciales.

Lines 237 et seq. (section 3.3): Taking into account that the BBNJ Agreement has meanwhile been formally adopted, section 3.3, whenever reference is being made to the 'draft agreement', needs to be updated.

Line 302: Taking into account that the ILC has taken the view that 'interpretative' COP decisions adopted by consensus, even if not legally binding as such, can be considered as subsequent agreements under Article 31 (3) (a) or subsequent practice under Article 31 (3) (b) of the VCLT, conclusion 7 is perhaps framed too broadly.

This is a well-written and logically structured chapter on international law and OAE. The author’s acknowledge the role of domestic law in the introduction, but the focus of this article is, by and large, on rules at an international level. The authors build off existing literature on CDR and international law to provide a contemporary analysis of pertinent rules and developments for OAE. Most notably, this chapter reflects on two recent developments that have yet to be considered in detail in the literature: the potential implications of the new BBNJ Agreement and efforts currently underway that could see OAE added to the list of activities regulated by the 2013 London Protocol Marine Geoengineering Amendment. In considering these developments, this article makes a fresh contribution to the literature on international law and the governance of marine CDR proposals (in addition to OAE specifically). The analysis itself is generally presented in a way that is accessible to non-legal experts, and the authors are fair to point out the limitations of existing rules, as well as issues that require further legal research.   

I nevertheless recommend that the authors address the following, minor issues prior to publication:

1. On page 3, around line 90, the authors suggest that international regulation of OAE “may need to be distinguished” based on the purpose of OAE (i.e. whether it is for CDR or for combatting ocean acidification). The reason for this suggestion is not apparent to the reader. If the technology is the same, and the environmental risks are the same, why would different governance be required for different purposes? This question is especially pertinent as the use of OAE for addressing one issue (i.e. CDR) will likely have co-benefits concerning the other (i.e. OA).
2. The audience of this chapter is intended to be broader than international lawyers. When talking about rights and freedoms under UNCLOS in various maritime zones, it is important to qualify for non-expert readers that these are subject to other obligations under that agreement, as well as other obligations under international law. For example, in Table 1, it states that “No State has sovereign rights. Freedom of the high seas applies and the zone is open for use to all states”. Statements like this need to be qualified for non-expert readers, to avoid giving a mistaken impression about the extent of rights and freedoms.
3. On page 6 at 140, the authors describe UNCLOS as a “framework agreement”, akin to the UNCBD and UNFCCC. There are significant differences between UNCLOS and these “framework” agreements, and some legal scholars would disagree with this characterisation. The authors should consider the explanation put forth by Alan Boyle in “Further Development of the Law of the Sea Convention: Mechanisms for Change” in this regard.
4. At conclusion 4 on page 9, the authors suggest that the LP assessment framework could inform the content of obligations under customary international law. Given the low level of state acceptance of this amendment to date, it is unclear why this would be the case. If the authors wish to pursue this argument, greater justification, including reference to relevant authority, is needed.
5. At the top of page 22, the authors state that, although the 2013 LP amendment is yet to enter into force, it appears to “have support within a fairly large segment of the international community”. Further evidence/justification is needed to support this claim, or it needs to be further clarified, especially as the low level of state acceptance suggests the opposite.
6. On page 22, the authors talk about the need for coherence. It would be helpful for non-legal experts to have an explanation of what this means and why it is considered important.
7. In the paragraph spanning lines 560-565, the authors make several normative claims, including that research should seek to minimise adverse social impacts and be designed to maximise benefits, ensuring equal distribution. I do not disagree with these claims, but they should be supported by reference to relevant literature on good CDR governance.
8. At conclusion 13, the authors refer to “established and developing principles surrounding international liability for operators and private actors”. It would be helpful if they could cite a few examples.
9. Double check that sources referred to in text are listed in the reference list, as this appears to be incomplete.