How do you prosecute a tanker that changed its flag nine times?

The Swedish Coast Guard boarded a sanctioned tanker linked to Russia’s shadow fleet on 3 April after discovering a 12-kilometer oil slick east of Gotland in the Baltic Sea, then released it a day later—investigators found insufficient evidence that the Flora 1 had caused the spill, the Associated Press reported.

The shadow fleet is built for flag-switching, name-changing, and ownership layered across jurisdictions that rarely cooperate.

Boarding a shadow fleet tanker turns out to be the easy part. Proving it committed a crime—in international waters, with a spill already dissolved into the sea—is harder. The shadow fleet is built for this: flag-switching, name-changing, ownership layered across jurisdictions that rarely cooperate. Against legal standards of evidence, the design held.

The boarding and the spill

Coast Guard aircraft detected the 12-kilometer-long mineral oil slick early on 2 April. The Flora 1 was nearby, sanctioned, and sailing from a Russian oil terminal on the Gulf of Finland. Early on Good Friday—3 April—operating under Operation Klöver alongside police, the Coast Guard boarded the vessel and escorted it to anchorage outside Ystad in southern Sweden, with 24 crew members on board.

This was the first time Sweden had traced a Baltic oil spill to a vessel already on the EU sanctions list.

Two were questioned and formally notified of suspected violations of laws against vessel pollution. Daniel Stenling, deputy operations chief at the Swedish Coast Guard, noted this was the first time Sweden had traced a Baltic oil spill to a vessel already on the EU sanctions list.

The oil slick could not be cleaned up. By the time authorities moved, it had already merged with the sea.

“The suspicions will not lead to prosecution, but shipping should know that Swedish authorities together uphold order at sea.”

Senior prosecutor Frida Molander said that the investigation had concluded and the criminal suspicion would not result in charges. Cameroon—whose flag status the Coast Guard had listed as “unclear” at the time of boarding—confirmed the vessel was registered in its maritime registry, and the Flora 1 was released the following day.

Stenling said in a statement: “The suspicions will not lead to prosecution, but shipping should know that Swedish authorities together uphold order at sea.”

Designed to evade

The Flora 1 is on both the EU’s and Ukraine’s sanctions lists. The EU designated it for “practicing irregular and high-risk shipping practices,” the AP noted. Ukraine’s National Security and Defense Council added it in December 2025 with a ten-year sanctions term covering asset freezing and a full trade ban.

Since 2023 alone, the vessel had cycled through the flags of Sierra Leone, Benin, Palau, Djibouti, Panama, Gabon, and St. Kitts and Nevis, according to Equasis, an international maritime shipping database cited by Dagens Nyheter. Over its full history, the vessel had changed its name up to six times and its flag up to nine, the AP noted.

The vessel had been observed disabling its automatic identification system, the transponder that broadcasts a ship’s position to others at sea.

The vessel had also been observed disabling its automatic identification system, the transponder that broadcasts a ship’s position to others at sea, and conducting ship-to-ship cargo transfers to obscure cargo origins. Its registered owner is based in Hong Kong.

Every feature that makes these ships hard to sanction also makes them hard to prosecute.

When boarding isn’t enough

In March alone, Sweden boarded the Sea Owl I off Trelleborg and the Caffa near the same port—the Caffa’s captain is now suspected of using false documents. In late February, Belgium and France seized a sanctioned tanker in the North Sea in Operation Blue Intruder. On 25 March, the UK authorized its navy to board sanctioned Russian tankers in British waters. The Flora 1 was the next in line.

Swedish authorities estimate that roughly 90% of Russia’s crude oil exports now travel by shadow fleet.

Each action sent a message that enforcement was closing in. The Flora 1’s release sends a different one—and it lands. At the same time, the Trump administration has issued waivers allowing Indian buyers to purchase Russian crude already at sea, a move US senators say undermines years of pressure on Russian exporters.

Swedish authorities estimate that roughly 90% of Russia’s crude oil exports now travel by shadow fleet—aging, often uninsured tankers operating in one of Europe’s most enclosed and ecologically fragile seas. Baltic states have warned for years that a major spill is a question of when, not if.

On 2 April, a 12-kilometer slick appeared east of Gotland. The vessel suspected of causing it sailed away.