Sabotage of submarine critical infrastructure (cables and pipelines) in the baltic sea, 2023–2025: the attribution problem and legal grey-zone gaps

Between October 2023 and early 2025 the Baltic Sea experienced a sequence of damaging incidents to submarine telecommunications cables and energy pipelines, from the Balticconnector gas pipeline and adjacent data cables to the C-Lion1, Estlink 2, and related cable breaks, most of them attributed in public debate to anchor-dragging by vessels linked to a sanctioned shadow fleet. This review synthesises the peer-reviewed literature published between 2019 and 2026 on three questions raised by these events: why the infrastructure is so vulnerable, why responsibility is so hard to attribute, and why international law struggles to prevent or sanction such acts beyond the territorial sea. A semi-systematic, thematic review method was applied across Scopus, Web of Science, and Crossref, supplemented by primary legal instruments and European Union and NATO documents, yielding forty-seven sources synthesised into four domains: the threat landscape, the attribution problem, the legal grey-zone gaps, and the emerging response. The review's contribution is an integrative attribution–accountability gap framework that joins three literatures usually kept apart, the maritime-infrastructure-security, the grey-zone and attribution, and the law-of-the-sea literatures, and traces a four-link chain from detection to attribution to legal characterisation to response, showing that Baltic subsea sabotage occupies a doubly permissive space in which an act is simultaneously hard to attribute and hard to sanction. The synthesis finds that physical vulnerability is structural and growing, that deniability is the deliberate design feature of grey-zone action rather than an incidental difficulty, that the United Nations Convention on the Law of the Sea protects the laying of cables and pipelines far better than it protects them from intentional harm, and that the institutional response is real but immature. The review concludes that closing the accountability gap depends less on new technology than on strengthened coastal-state jurisdiction, evidentiary cooperation, and a resilience-by-design posture, and it identifies the absence of an agreed legal threshold for sabotage below the use of force as the field's central unresolved problem.