The Research Institute for Democracy, Society and Emerging Technology (DSET) National Security Program today (August 20) released a new report, “Undercurrent: Limits and Prospects of Submarine Cable Security for Taiwan.” The report examines Taiwan’s vulnerabilities in protecting submarine cables and offers policy recommendations, urging allied nations to strengthen law enforcement cooperation with Taiwan.
The launch event featured a briefing by the report’s author, Ta-Chen Chen, DSET Non-Resident Fellow, former staff member of Taiwan’s National Security Council, and currently an S.J.D. candidate at George Washington University Law School. Commentary was provided by Kenny Huang, Taiwan Network Information Center (TWNIC), and Wen-Ling Hung, Associate Professor at National Kaohsiung University of Science and Technology and former Deputy Minister of the Ocean Affairs Council.
Chen highlighted Taiwan’s first-ever prosecution of submarine cable damage in the Hong Tai 58 case, ruled by the Tainan District Court in June. While the case was widely viewed as a landmark case, Chen noted that it fell short of addressing the broader challenges posed by “gray zone” activities. Prosecutors struggled to apply Taiwan’s new national security provisions under the Telecommunications Management Act, as they could not prove foreign direction or establish direct intent. The court ultimately ruled on indirect intent, underscoring the difficulty of proving malicious intent under current intelligence and legal frameworks.
“The case illustrates Taiwan’s limited capacity to attribute intent in gray zone operations,” Chen said. “This gap prevents existing legal tools from being fully effective and therefore highlights the need for stronger cable protection policies.”
The report reviews existing proposals for enhancing submarine cable security, which fall into three categories: expanding coastal state jurisdiction, improving intelligence capabilities, and strengthening international cooperation. However, Chen emphasized that each approach faces significant legal and operational constraints.
In light of the identified constraints, this report proposes three policy tracks to address submarine cable damage on the premise of perceived gray zone activities: punish, offset, and address.
First, regarding “punishment,” policymakers must first obtain concrete intelligence to establish both the factual and legal attribution of the vessels involved to the gray zone actor state. Policymakers may then invoke countermeasures under customary international law to prevail over the existing limits on coastal state jurisdiction beyond the territorial sea under international law, and exercise unilateral jurisdiction over the vessels involved.
Second, regarding “offset,” when constrained by limited intelligence and international norms, policymakers should inventory feasible unilateral policy measures or coordinate with allies in shared international forums to impose higher regulatory burdens on the gray zone actor state (for example, stricter port state measures, cooperation through the IMO, etc.), ultimately offsetting the intended political gains of the gray zone actor state.
Finally, regarding “address,” policymakers should draw on contemporary models of international coordination over the flag state’s exclusive jurisdiction in international waters. Policymakers should first hold the flags of convenience accountable for the vessels involved, and through international coordination, request these flag states to propose proper regulation and punishment for submarine cable damages agreed upon by the international coordination. These international coordinations should also aim to acquire prior consent from these flag states to allow the member states of the international coordination to exercise jurisdiction and conduct investigations over the vessels involved in cases involving submarine cable damage. Under this policy track, policymakers should work with allies to gradually secure the prior consent of most of the relevant flags of convenience states in cases of submarine cable damage, ultimately reducing the room for maneuver for the gray zone actor states.
Chen stressed that recent cases demonstrate the limits of relying solely on domestic regulatory amendments to counter emerging threats. He underscored the need to prioritize stronger international coordinations with allied nations, which would place higher regulatory obligations on flag states and establish joint law enforcement regimes based on flag states’ consent. He noted that the U.S. Congress has already introduced proposals on submarine cable protection, while Taiwan–Europe discussions on the issue have also gained momentum in recent months. Taiwan and its partners, he urged, must move swiftly and place the right focus to advance such agreements.
Commenting on the report’s recommendations, Kenny Huang, Chairman of the Taiwan Network Information Center (TWNIC), emphasized that submarine cables connecting the world are the lifeline of modern communications and finance, yet remain highly vulnerable. Existing international maritime law provides insufficient protection. The study puts forward three recommendations—punish, offset, and address—aimed at remedying the shortcomings of current law, exploring new modes of international cooperation and practical measures to confront evolving external challenges, thereby enhancing the protection of these critical infrastructures.
Hung Wen-ling, Associate Professor at National Kaohsiung University of Science and Technology and former Deputy Minister of Taiwan’s Ocean Affairs Council, noted that the report underscores how the primary threats facing Taiwan’s submarine cables are not traditional military attacks, but rather the legal and political challenges posed by “gray-zone” operations. This shifts the focus beyond physical security to the governance and legal gaps that adversaries can exploit. The report’s pragmatic solutions do not call for drafting new international law, but instead propose an “address” strategy—leveraging a multilateral, flag state–based mechanism to constrain malicious actors in a practical manner without escalating tensions. At the same time, this approach creates opportunities to bring in new stakeholders, such as international cable operators and law enforcement agencies, to establish fresh norms through regional cooperation.
In the first round of Q&A, a question was raised about whether lessons could be drawn from the Baltic Sea’s experience with Russia’s “shadow fleet.” Report author Ta-Chen Chen responded that gray-zone operations often exploit the relative limitations of coastal state jurisdiction in international waters. Without concrete evidence, however, coastal states remain unable under international law to unilaterally extend their jurisdiction into international waters, and international coordination or rule-making efforts face difficulties in building consensus.
While Taiwan has had successful detection and prosecution cases within its territorial waters, the rulings have not yet clarified the nature of the presumed gray-zone activities. For this reason, Chen stressed, “evidence” remains the foundation for establishing legal attribution and shaping policy. On the Coast Guard’s monitoring capacity, Chen explained that Taiwan already possesses robust surveillance and enforcement capabilities within its territorial waters, and past cases show that tracking suspicious vessels poses no difficulty. He emphasized, however, that even though Taiwan can conduct sustained monitoring in international waters, jurisdictional limits continue to apply.
Associate Professor Wen-Ling Hung added that enhancing comprehensive monitoring will require significant technological investment and institutional reform. The key, she noted, is whether the Coast Guard can effectively integrate civilian and defense resources, with legislative support, to establish new systems and long-term visions that strengthen national security resilience.
In the second round of Q&A, discussions turned to the scope of submarine cable issues, information sharing, and legal reforms. Chairman Kenny Huang pointed out that although most of Taiwan’s submarine cables are owned by Chunghwa Telecom, their dual military-civilian nature means that regardless of who builds or operates them, they are fundamentally national security concerns. Taiwan, however, still lacks specialized cable repair vessels and must rely on international cooperation and shared capacity.
Chen stressed that the most urgent need in international cooperation lies in intelligence sharing, which can clarify the full picture of cable disruptions, serve as a starting point for building policy consensus, and improve attribution capacity. On the legal and policy front, he proposed three pathways: first, relying on existing international law principles, coastal states could unilaterally exercise jurisdiction over vessels involved in incidents on the high seas, but this carries a high evidentiary threshold under international law; second, making flexible use of existing domestic policies to reduce the political gains of gray-zone actors; and third, advancing new regional cooperation mechanisms, which, given the wide scope of agencies involved, would need to be coordinated at the National Security Council or presidential level.
Hung added that Taiwan should consider whether to accept indirect evidence and also review the effectiveness of current information-sharing platforms. She emphasized that as a key maritime nation in the region, Taiwan should demonstrate greater ambition and determination, actively positioning itself as a regional hub for submarine cable maintenance and security in East Asia.
Read the Full Report: Undercurrent: Limits and Prospects of Submarine Cable Security for Taiwan