The European Union is establishing legal grounds to halt at least 16 dodgy oil tankers if they enter the Baltic Sea. The catch: these ships have no flags at all.

Internal EU documents leaked to EUobserver show Brussels plans to blacklist 120 more Russian oil tankers in its 19th sanctions round, bringing the total to 568 vessels. The listing bars them from EU ports and blocks European firms from providing insurance or bunkering services.

Why previous sanctions failed

Previous sanctions achieved little. Shadow fleet ships never called at EU ports anyway, and they sailed freely through Baltic waters under "innocent passage" rights guaranteed by the 1994 UN Convention on the Law of the Sea and the 1857 Treaty of Copenhagen.

But 16 of the newly listed ships operate without any recognized national flag, according to the leaked files and the Eqasis maritime database.

Article 110 of the UN convention on the Law of the Sea, however, allows states to intercept stateless vessels. The ships include the Adonia, Apate, Apus, Aquilla II, Bolu, Briont, Ethera, Everdine, Leona, Manaslu, Myra, Nemrut, Omni, Samos, Tagor, and Tassos.

Enforcement won't be simple though. When Estonia's navy tried stopping the stateless cargo ship Jaguar on 13 May, Russia sent an Su-35 warplane into Estonian airspace until the ship left the maritime zone.

France sets precedent with detention oil tanker

France demonstrated the new enforcement approach on 1 October by detaining the previously blacklisted Boracay tanker and arresting two crew members for allegedly using a fake Benin flag. Russian President Vladimir Putin called it piracy. Meanwhile, French President Emmanuel Macron announced more such actions would follow.

"We've decided to take a step forward by adopting policies to impede suspicious ships in our waters," Macron said in Copenhagen, adding that EU and NATO military chiefs would draft a new "policy of obstruction."

EU states and the UK are applying diplomatic pressure on flag-issuing countries to delist sanctioned vessels, according to Michelle Wiese Blockman from Windward shipping consultancy.

The main flag-issuers for the 120 newly blacklisted ships include Palau with 13 vessels, Panama with 11, and Comoros with 7.

Blockman noted that Barbados previously had over 100 shadow fleet tankers but now maintains around 25 after deleting sanctioned vessels from its registry. Gabon showed a similar reduction from over 100 ships in 2024 to approximately 25.

Fraudulent registries of ships emerge as new threat

Here's the problem: fraudulent registries. Windward has identified 13 fake registries that issue licenses through websites. An estimated 62% of sanctioned tankers now use false flags, according to Blockman.

"They're effectively lawless and outside of the international rules-based order," she said.

Most sanctioned ships carry inadequate or fake insurance. If a major spill occurs, EU states foot the bill.

"If there's a $1bn oil spill - who'll pick up the cost?" Blockman asked. "Good luck trying to get it from the bloke who owns the ship on paper - it's probably a nominee director, who couldn't afford the $35m that the ship cost in the first place."

The ownership structures hide the real owners through up to seven layers of shell companies in opaque jurisdictions.

David Osler from Lloyd's List said: "It's beyond the ability of most mere mortals to get to the bottom of these outfits."

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Russia weaponizes shadow fleet

Artem Voitovych from Kyiv-based Olgian Strategies told EUobserver that Russia was weaponizing its shadow fleet.

"If the Russians can make such a use of their shadow fleet, they will do it without any reservations," he said. "All shadow fleet oil tankers should be seized, with malice and without any fear of Russian or Chinese retaliation."

Ukraine has requested that four additional vessels be added to the sanctions list: the Anlan, Ionian Sailor, Oceanid, and New Pride.