UK Authorizes Military Action Against Sanctioned 'Shadow Fleet' Vessels

The United Kingdom has authorized its armed forces to board and detain sanctioned vessels operating in "shadow fleets" within British waters, utilizing powers under the Sanctions and Money Laundering Act 2018. This development follows the transit of dozens of UK-sanctioned oil tankers, attributed to Russia's "shadow fleet," through the English Channel, despite previous UK commitments for assertive action. Internationally, various nations, including Pacific Island states, are intensifying monitoring and enforcement measures against these vessels, which are suspected of circumventing oil sanctions imposed after Russia's full-scale invasion of Ukraine.

The Rise of the 'Shadow Fleet'

The "shadow fleet" consists of commercial ships, typically older tankers, that often engage in deceptive shipping practices, may lack Western insurance, and operate with obscured ownership structures. This fleet expanded significantly after Western nations imposed a price cap on Russian oil following its invasion of Ukraine, enabling the shipment of sanctioned oil.

These vessels are primarily used to transport Russian crude oil to China, India, and Turkey. According to the Center for Strategic and International Studies (CSIS), shadow fleet tankers transport between $87 billion and $100 billion worth of oil annually. An analyst from the Centre for Research on Energy and Clean Air reported that 68% of all Russian crude oil was transported on sanctioned tankers in December 2025.

The "shadow fleet" consists of commercial ships that often engage in deceptive practices, may lack Western insurance, and operate with obscured ownership structures, transporting an estimated $87 billion to $100 billion worth of oil annually.

UK's Assertive Stance and Actions

The UK government has authorized its armed forces and law enforcement to take direct action against ageing tankers using false national flags or opaque ownership structures in British waters. Ministers believe the Sanctions and Money Laundering Act of 2018 provides the legal basis for military force against sanctioned vessels not legitimately flagged.

Ministers believe the Sanctions and Money Laundering Act of 2018 provides the legal basis for military force against sanctioned vessels not legitimately flagged.

Foreign Secretary Yvette Cooper stated in January that the British government was prepared to "tighten the chokehold" on Russia and implement new "assertive actions" against shadow fleet vessels.

Indeed, dozens of UK-sanctioned oil tankers have transited the English Channel. BBC Verify tracked 42 such vessels passing through the Channel after the UK government reportedly received legal assurances earlier in the month that these vessels could be detained. Additionally, six tankers operating under false flags were identified in the Channel by BBC Verify since the start of January.

The UK has previously collaborated with allied forces in operations against such vessels. In January, British armed forces assisted US troops in the seizure of the Marinera oil tanker in the North Atlantic, which US officials stated was carrying oil for Venezuela, Russia, and Iran. The UK also supported US forces in the pursuit and seizure of the tanker 'Bella 1' (renamed 'Marinera') near Iceland and aided France in a tanker seizure in the Mediterranean.

International Scrutiny and Enforcement

Monitoring efforts against the shadow fleet are intensifying across European waters and beyond.

European Waters

• Baltic Sea: Swedish Coastguard officers routinely contact oil tankers for information on insurance, flag state, and last port of call. Estonia's navy has reported an increase in these vessels transiting past Estonia to major Russian oil terminals. Finland, Sweden, and Estonia, members of the UK-led Joint Expeditionary Force (JEF), have conducted operations targeting suspected shadow fleet vessels.
• Germany: The Arcusat, previously sanctioned by the US as the Tia, passed through the English Channel on January 8 before being intercepted by German federal police and turned away from German waters.

Pacific Island Nations Take Action

Following increased scrutiny, Pacific Island registry administrators have begun de-flagging sanctioned vessels and tightening regulations.

• Cook Islands: Deregistered the Eagle S after EU sanctions and removed nearly 190 of 214 tankers registered since 2022, including 53 for sanctions and 135 for non-compliance. It has prohibited its flagged vessels from operating in the Baltic Sea and banned those carrying Russian, Iranian, or Venezuelan petroleum products.
• Palau: Screens vessels against sanction lists and intends to enhance registry oversight. It recently concluded its arrangement with its private shipping registry operator after deregistering shadow fleet tankers.
• Vanuatu: Updated its sanctions policy in October to apply EU and UK sanctions, in addition to UN and US listings, leading to the deletion of four vessels with "sanctions-related concerns."

Navigating the Challenges: Characteristics of the Shadow Fleet

Monitoring shadow fleet vessels remains challenging due to several strategies employed:

• False Flags and Identity Changes: Many vessels operate without valid national flags, become stateless, or use false flags. The number of falsely flagged ships globally has more than doubled to over 450, primarily tankers, according to the IMO database. Vessels frequently change names and claim flags from multiple countries, including those without official maritime registries like Lesotho.
• Obscured Ownership: The beneficial owners of 60% of shadow fleet vessels remain unidentified, utilizing opaque ownership structures to avoid detection.
• Disabled Tracking Signals: Vessels deactivate tracking signals or broadcast false locations.
• Aging Infrastructure: Many vessels in the fleet are aging, and the absence of proper insurance raises concerns regarding accountability and financial responsibility in the event of incidents like oil spills.
• Jurisdictional Limits: While political discussions focus on strengthening actions, the authority of navies and coastguards to intervene diminishes further out at sea, constrained by the principle of navigation freedom. Stateless vessels are technically not afforded the right of innocent passage.

Key Incidents Involving Shadow Fleet Vessels

• Sofos: Sanctioned by the UK Foreign Office in May 2025, it traveled through the Channel after a journey from Venezuela and is now near St Petersburg, Russia. Its tracking signal was deactivated near Venezuela, with satellite imagery confirming its presence at Jose oil terminal before reactivation.
• Nasledie: Also sanctioned by the UK in May 2025, this tanker, over 20 years old, was renamed from Blint and switched to a Russian registry. It entered the Channel in January carrying approximately 100,000 tonnes of Urals crude oil.
• Unity (formerly Ocean Explorer, Ocean Vela, Beks Swan, March): This vessel, originally built in 2009, has traversed the English Channel four times in the last twelve months. It was cited in a 2018 UN report for alleged involvement in ship-to-ship transfers with a sanctioned vessel. It was removed from the Marshall Islands registry in 2024 after its operator and beneficial owning company were sanctioned by the UK. Unity was added to the UK and EU's list of sanctioned vessels earlier in the year and has reportedly experienced mechanical issues, seeking shelter in the Channel following a mechanical failure and being detained at a Russian port due in part to unpaid wages.
• General Skobelev: A Russian warship reportedly escorted this sanctioned tanker through the Channel on January 20.

Reactions and Geopolitical Concerns

Dame Emily Thornberry, chair of Parliament's Foreign Affairs Select Committee, expressed disappointment regarding the lack of interceptions, emphasizing the need for effective sanction implementation.

Russia has cautioned that direct actions against its-linked vessels could escalate into direct conflict. On January 15, Russian foreign ministry spokeswoman Maria Zakharova stated:

"Any detention of the tankers would be considered a violation of international law that would harm Russian interests."

A senior Russian official further stated that Moscow might deploy its navy to protect such vessels, referencing what was described as 'western piracy.'