Braving the Storm: Countering Shadow Fleet Operations in Europe Policy Brief Executive Summary & Recommendations

Author: Dr. Victoria VDOVYCHENKO, PhD, Joint Programme Leader, Future of Ukraine Programme, Centre for Geopolitics, University of Cambridge
Expert contributions:
Captain (N) Kurt ENGELEN, Centre for Security and Defence Studies
Dr. Ian RALBY, Auxilium Worldwide
Petras KATINAS, Centre for Research on Energy and Clean Air
Prof. Nick CHITADZE, International Black Sea University
Andriy KLYMENKO, Head, Monitoring Group at the Institute for Black Sea Strategic Studies

On the occasion of the Ukraine Recovery Conference that was held in Rome on 10–11 July 2025, the Centre for Geopolitics at the University of Cambridge, in partnership with ECFR, CREA, and LUISS, was honoured to host a high-level roundtable titled “Breaking the Chain: Countering Shadow Fleet Operations in Europe’s Strategic Waterways”. The event contributed to the wider Ukraine Recovery Conference by examining a critical dimension of Russia’s war against Ukraine: the economic infrastructure underlying the conflict and the maritime security challenges it creates for Europe. Drawing on the latest data and expert insights, the discussion analyzed the effectiveness of existing economic measures targeting Russia and their implications for conflict resolution and European security.

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The so-called ‘shadow fleet’ remains a critical enabler of the Russian Federation’s ability to sustain oil revenues in the face of extensive international sanctions.

Despite intensified enforcement efforts by the European Union (EU), NATO member states, and like-minded partners, a significant portion of Russia’s maritime oil exports continues to operate through a network of opaque and evasive practices. This fleet—comprising tankers with concealed ownership, frequent flag changes, disabled AIS transponders, and widespread use of ship-to-ship (STS) transfers—now accounts for more than one-third of Russia’s seaborne oil exports.

While coordinated efforts to curb the fleet’s operations have made incremental progress—including in sanctions designations, port-state controls, and increased awareness of environmental and hybrid security risks—these measures remain insufficient given the evolving complexity and transboundary nature of the threat.

Moreover, growing uncertainty regarding the continuity and scope of U.S. sanctions policy places additional responsibility on European actors to ensure consistent and forward-looking enforcement mechanisms.

The capacity of the EU and its allies to respond with timely, coordinated, and adaptive measures is therefore of strategic importance.

This policy brief outlines a set of strategic and operational recommendations emerging from the high-level roundtable “Breaking the Chain: Countering Shadow Fleet Operations in Europe’s Strategic Waterways,” convened as an official side event of the Ukraine Recovery Conference (URC) in Rome on 9 July 2025. Drawing on expert contributions from Ukraine, the United Kingdom, Lithuania, Georgia, the United States, Canada, and Italy, the discussions emphasized the need for stronger legal instruments, enhanced maritime surveillance, and more harmonized cross-jurisdictional coordination.

The brief offers pragmatic proposals across two thematic pillars:

1. Strategic deterrence and economic disruption of illicit maritime networks (so-called “Strategic Level”).

2. Strengthening sanctions enforcement and enhancing maritime domain awareness (so-called “Operational Level”)

A comprehensive policy paper will follow, synthesizing the roundtable’s deliberations and key areas of consensus.

Strategic Level:

Identify a common approach to identifying the criteria for a “shadow fleet” vessel.

The “shadow fleet” is a colloquial term for a perceptible phenomenon, but currently, there is no agreed definition. Any action to address the shadow fleet should start with a clear, generally agreed set of measurable criteria that can be used to consistently designate which vessels are and are not part of this phenomenon. Only with that clarification can rigorous and meaningful action be taken by defense, security and law enforcement officials. Until that time, there is a risk that one state or another will take enforcement action on what they think might be a “shadow fleet” vessel, make a mistake in the process, and suffer legal and political blowback as a result.

Additionally, all states must be careful not to diminish the principle of free seas by impeding the freedom of navigation with an arbitrary approach to intervening in voyages of commercial vessels. The consequence of doing that may be for Russia and other hybrid aggressors to use similar arguments to restrict freedom of navigation elsewhere. Clarity and commonality in the definition can help avoid such a tu quoque problem.

Establish a Joint Maritime trilateral EU–NATO–JEF Coordination mechanism:

With an objective to reduce redundancy and ensure complementarity between the regulatory, strategic and operational levels, the EU, the Joint Expeditionary Force and NATO, three actors that find themselves involved in countering the Russian shadow fleet should streamline and coordinate their respective efforts and actions. Fields that could benefit from alignments include deconflicting naval operations, fusion of lists of blacklisted ships, sharing and establishing standardized inspection protocols, creating a centralized dynamic databank of incidents with non-compliant ships to make reflagging more difficult.

An appropriate EU body—such as the European Defence Agency’s Maritime Surveillance (MARSUR) initiative or a similarly mandated institution—should be formally designated to lead the tracking and analysis of shadow fleet operations. This entity could engage with technology firms as strategic partners to help fuse insights and enhance vessel identification and monitoring capabilities. Leveraging advanced satellite imagery, Automatic Identification System (AIS) data, Radio Frequency Identification (RFID), and AI-driven analytics, the agency would be well-positioned to develop a comprehensive and continuous oversight mechanism targeting illicit maritime activities linked to sanctions evasion.

Develop practical guidance for both EU and non-EU member states to enforce maritime sanction.

One of the biggest challenges for sanctions enforcement is that maritime forces – primarily tasked with other responsibilities – lack clear operational guidance on what they should do with regard to a sanctioned vessel in different maritime zones. The mix of unilateral and multilateral sanctions further confuse the matter. The territorial sea, contiguous zone and high seas each present different enforcement challenges for addressing sanctioned vessels and concrete, operational-level guidance is desperately needed. Additionally, coordination with legal officials for prosecution and adjudication of cases is critical. Many states are hesitant to seize assets that could turn into liabilities for the state, so a common approach with mutual support could pay dividends in the frequency and impact of enforcement actions.

Strengthen coordinated sanctions and apply diplomatic pressure on flag states to deregister non-compliant ships.

European policymakers should intensify efforts to designate additional shadow fleet vessels under EU sanctions. While the inclusion of hundreds of vessels in the EU’s 17th sanctions package (adopted on May 20) is a positive step, its effectiveness will remain limited without synchronized action. Greater transatlantic alignment is therefore essential to close enforcement loopholes and meaningfully constrain Russia’s ability to bypass oil export restrictions.

At the European Union level, this necessitates: (1) the allocation of additional resources to enforcement bodies to ensure more robust and consistent implementation of sanctions, and (2) the institutionalization of a more flexible and continuous designation process, moving beyond reliance on periodic sanctions packages to enable timely and scalable responses.

Anticipate and prepare for increased Russian naval involvement in ‘shadow fleet’ operations.

European and NATO decision-makers must not allow heightened Russian military posturing to weaken enforcement resolve; however, they must also recognize the diminishing margin for operational error. On the same day Russian forces detained the Green Admire, a Russian naval vessel escorted the Sirtaki, a Marshall Islands–flagged tanker, from Kaliningrad to St. Petersburg. Finland’s Defence Minister Antti Häkkänen confirmed on May 24 that Russian shadow fleet tankers are now receiving direct military escort in the Gulf of Finland. Whether this becomes routine or remains episodic, European governments must treat it as a credible threat scenario and develop clear protocols for monitoring and potential interdiction of such dual-use maritime activity.

Prepare to anticipate potential Russian retaliation.

Russia’s increasingly assertive maritime behaviour—such as the military escort of commercial vessels through European waters—suggests that enforcement measures will provoke a response. EU and NATO decision-makers must anticipate potential Russian retaliation and clearly communicate that European critical infrastructure and maritime sovereignty are non-negotiable.

Based on national legislation, regional NATO member states could consider enacting prohibitions

on the navigation and/or presence of commercial vessels within their territorial waters if such vessels are assessed to pose a threat to critical underwater infrastructure in the Baltic Sea.

The uninterrupted functioning of underwater infrastructure in the Baltic Sea is of vital importance not only to the national security and defense of regional NATO members, but to the security of the Alliance as a whole. Given that such infrastructure has already become the target of hostile activity, concerned coastal states are entitled—under Article 51 of the UN Charter, which affirms the right to individual and collective self-defense—to adopt a range of defensive measures, including legal and regulatory actions.

Baltic Sea countries—particularly Denmark, which controls critical maritime straits—should formally express grave concern over recent Russian tanker incidents in the Black Sea. Given these risks, Baltic nations have legitimate grounds to declare that, starting from a specified date, tankers listed on the blacklists of the Paris Memorandum of Understanding (of which Baltic states are members) and other relevant port state control memoranda (where they are associate members) will no longer be permitted entry into the Baltic Sea.

Note: For instance, even a spill of just 8,000 tons of fuel oil resulted in contamination of hundreds of kilometers of coastline. In the event of a single crude oil tanker accident in the much smaller Baltic Sea, the spill could reach up to 160,000 tons, with far more severe ecological consequences.

Establish a declaration – signable by any state – clarifying the criteria of the “shadow fleet” and designating it a per se threat to the peace and good order of a coastal state.

Innocent passage is allowed in any state’s territorial waters as long as that passage is continuous, expeditious and without prejudice to the peace and good order of the coastal state. Given the conduct of the shadow fleet, if states all declare that the shadow fleet, defined by a consistent set of objective criteria, is inherently a threat to the security and good order of the coastal states, it denies the fleet the claim of innocent passage. This also provides coastal states with a valuable tool in going after the vessels that enter their territorial seas.

To ensure that sanctions targeting Russian oil tankers effectively impact the export flow of seaborne Russian crude, the current sanction model must be revised.

Specifically, restrictions should not be limited to access to ports in sanctioning countries but must also extend to the territorial waters of those states.

Under such a revised framework, sanctioned tankers would be prohibited from transiting key maritime chokepoints such as the Danish Straits and the straits between France and the United Kingdom. Otherwise—as evidenced by developments over the past two to three months—existing sanctions remain largely symbolic for vessels whose primary destinations include India, China, Singapore, and several African states.

Operational Level:

Align designation lists across sanctioning jurisdictions.

As of June 2025, the EU, UK, and US have collectively sanctioned a total of 464 vessels linked to Russia’s oil trade. However, only 34 vessels appear on all three sanctions lists, while 211 vessels are designated by two of the three entities.

This fragmented approach highlights a critical lack of coordination among sanctioning authorities and suggests that coordinated multilateral sanctions are significantly more effective in curbing shadow fleet activity than fragmented or unilateral actions.

Ban ship-to-ship (STS) transfer in the EU member states territorial waters.

While the overall number of ship-to-ship (STS) operations in EU member states territorial waters has declined, enforcement gaps persist. These operations not only pose a serious compliance risk that undermines the sanctions regime but also present a significant ecological threat. Shadow tankers often operate under poor safety standards, lack adequate insurance, and conduct transfers under unsafe conditions, increasing the risk of oil spills and maritime accidents in sensitive coastal areas. Additional reminders to key partners outside of the EU as to the legal requirements for an STS under MARPOL may also help encourage other states to take enforcement action.

Ensure full compliance with the International Maritime Organization (IMO) fuel quality standards

All vessels operating within EU member states waters, especially in designated Sulphur Emission Control Areas (SECAs), must strictly abide by the IMO fuel quality standards as outlined in MARPOL Annex VI. This includes using fuels that meet the mandated sulphur content limits and other quality criteria to minimize harmful emissions such as SOₓ and particulate matter.

Enhance transparency and compliance in maritime insurance through IMO guidelines

To strengthen the integrity of maritime operations, it is imperative that the International Maritime Organization (IMO) revises its guidelines to enhance transparency regarding maritime insurance. The IMO should mandate that flag states require shipowners and insurers to publicly disclose key financial information, including insurer solvency data, credit ratings from recognized agencies, and audited financial statements. Additionally, IMO should be encouraged to clarify the requirements of “genuine link” for the purpose of registering a vessel.

Inspect and detain ships that do not comply with maritime requirements

Armed with the guidance noted above, port, coastal and flag states should intensify efforts to monitor and detain shadow fleet vessels that clearly violate maritime law, such as those unflagged, those failing to meet safety and environmental standards, or those posing clear security risks. Authorities must enforce environmental and navigation laws within their territorial seas, investigating and boarding suspicious vessels when justified. Crews involved in criminal activity should face prosecution, with noncompliant ships and personnel subject to international arrest warrants.

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This publication has been produced with the support of the European Endowment for Democracy (EED). Its contents do not necessarily reflect the official opinion of EED. Responsibility for the information and views expressed in this publication lies entirely with the authors.