Law of the Sea Comes Into Play in Hunt for Sanctioned Russian Oil

Ukraine's Western Allies Use Maritime Law to Inspect Russian Shadow Fleet Tankers

Until US President Donald Trump reversed the Russian oil embargo policy on Friday, Ukraine's Western allies were stepping up their use of international law.

Experts told Al Jazeera that the countries embargoing Russian oil for the first time this year applied boarding and inspection rights under the law of the sea.

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"The whole idea now is to make it more disruptive, deterrent, and more expensive for Russia to logistically get its oil to market on these ships, and that's definitely happening," said Michelle Bookman, an analyst at the maritime intelligence firm Windward.

Some Russian officials believe worse is to come.

"Western countries are trying to organize the interception of our ships. London and Brussels are drawing up plans to blockade the Baltic Sea and the straits leading to it. Other important shipping routes are also under threat," Nikolai Patrushev, head of the Russian Maritime Board, told officials during a visit to China on October 12.

Western sanctions not only prohibit the purchase of Russian oil in the embargoed territories. They prohibit insured Western tankers from selling Russian oil to third parties except at below-market prices, leaving Russia with little or no profit.

Since the imposition of sanctions in 2022, Russia has exported about half of its crude oil via a "shadow fleet" of tankers that are not owned or insured by Western entities and often do not meet environmental and safety standards.

It is the right to enforce these standards that allows the US, UK and EU to increase compliance inspections using Article 110 of the United Nations Convention on the Law of the Sea (UNCLOS), which allows coastal states to inspect ships.

This has reduced Russia's room to maneuver in a cat-and-mouse game to circumvent the oil embargo, 45 months after sanctions were imposed by the European Union, the United States and other Group of Seven (G7) countries.

"Many of these vessels were using false registrations and were stateless," Bookman said. "Instead of just greeting them, 'Hey, what's your flag?'" he said, according to UNCLOS. What's your insurance?' And then let them go merrily on their way under the right of innocent passage ... They now had a legal basis for boarding them."

Shadow tankers have engaged in various illegal activities that have exposed them to suspicion and boarding. They have transferred Russian oil from one ship to another on the high seas to hide its origin. They have turned off their trackers, falsified their locations, evaded insurance obligations and raised false flags to avoid surveillance.

The catalyst for the use of Article 110 against these measures was the United States, which late last year used it to board ships that were evading US Treasury Department sanctions against Venezuelan oil exports in Operation Southern Spear.

With Britain's help, the US Marines seized the Russian-owned Bella I in the North Atlantic last January, which had been sanctioned for carrying Iranian and Venezuelan oil, as well as Russian oil.

Britain and France have since boarded several more ships under UNCLOS. Although these inspections are small compared to the hundreds of shadow tankers afloat, they have put pressure on the shadow fleet, experts say.

"Article 110 was just sitting there, it didn't really have any traction," said Kristina Sieg, a professor of economic law at Aalborg University in Denmark. "The tool has always been there, but it never came out of the drawer."

This new adherence to the law has had adverse effects on the shipping industry.

"Effort has become the biggest headache in ship management," says George Giradakis, a maritime consultant who sits on the board of several shipping companies in Piraeus, Greece.

He told Al Jazeera that ship lessors and buyers "must thoroughly check that a ship complies with international standards," noting that "the need for time has increased several times compared to 2025."

Sanctioning nations have relentlessly pursued the Shadow Fleet.

After being kicked out of the Western Fleet, Russia switched to flags of prosperity. The EU, UK and US approached those registries and convinced them to kick out the shadow vessels.

"St. Kitts and Nevis was the first in early 2024 ... Palau, Gabon, Gambia, Cook Islands, San Marino, Barbados, Comoros, Guinea-Bissau, Sao Tome — they're all on hold," Bookman said.

Russia reacted this year by importing many of these tankers into its registry.

It lists 340 dark or shadow tankers as Russian flagships. Sanctioning countries have responded by using UNCLOS.

Ukraine wants all of Russia's export revenue from fossil fuels cut, and President Volodymyr Zelensky has warned that Trump's rapprochement with Moscow will prolong the four-and-a-half-year-old Russia-Ukraine war.

Kiev has attacked at least 26 of Russia's 30 refineries this year, causing pain in the global market.

The Center for Research on Energy and Clean Air (CREA) calculated that Russia saw an initial loss of 31 billion euros ($35 billion) this year after blocking the Strait of Hormuz in the Middle East, which pushed up oil and gas prices worldwide.

The windfall temporarily halted a steady decline in Russia's oil and gas revenues since the start of the Ukraine war in 2022. Monthly income increased by 52% in March.

But Russia's August earnings from crude oil, refined products and gas all fell 8 percent, following a 12 percent drop in July and a 1 percent drop in June.

The double weapon of UNCLOS and national laws

The official reason for the inspections is safety, Breisig said, and under UNCLOS "we have a right, we actually have a shared obligation to try to help each other control it."

But the agenda driving the inspections — stopping Russia's war of aggression in Ukraine by blocking Russian oil trade — is not enforceable under UNCLOS, he said.

"We are not allowed to tell some countries that they cannot export goods. The only body that can do that is the United Nations," he said. "To implement sanctions, you must have government authority."

This combination of national and international laws makes Denmark and Sweden very important.

Together, they control the narrowest points in the Baltic, where ships must pass to enter the North Sea and the Atlantic Ocean. So tankers loading crude oil and oil products at the Ust-Luga and Primorsk refineries in the Leningrad Region must pass through the territorial waters of Denmark and Sweden, where national laws apply in full, to reach global markets.

The Danish Maritime Authority recorded 292 transits of Russian shadow tankers through the Baltic Sea in 2025 and gradually tightened its inspection regime. In February 2025, Danish authorities began compliance inspections of tankers moored off the coast of Skagen, and in April seized the Vietnamese-flagged Shadow tanker Vigo after it was found to have poor fire safety.

In October, Denmark expanded inspections to include peak systems, fuel quality, emissions, waste management and certification.