The Strait of Hormuz is successfully closed. Because the starting of the battle involving the US, Israel and Iran on Feb. 28, 2026, oil tanker site visitors by means of the world’s most important oil transport choke level has collapsed, dropping by greater than 90%.
Iran has threatened to destroy any ships, together with oil tankers, that go by means of the strait from the oil depots of the Persian Gulf to the Arabian Sea and the remainder of the world. Corporations that insure ships towards the dangers of touring in conflict zones are deciding whether or not to subject protection on an individual-ship foundation. The worldwide physique that units many transport rules has advised ships’ crews that they’ve the appropriate to refuse to sail into the world.
As of March 6, greater than 400 tankers have been stranded within the Persian Gulf, with out permission from their homeowners to maneuver.
However some vessels are nonetheless transiting the strait. Many of the ships nonetheless transferring are those who function outdoors the foundations.
In maritime circles, these vessels are known as the “shadow fleet.” They’re vessels that ignore worldwide restrictions on commerce with sure nations, violate anti-pollution rules, smuggle unauthorized items or don’t need their cargo or actions too intently monitored.
They exist, even in a world stuffed with digital monitoring, as a result of the world’s oceans aren’t ruled the identical method the land is. On land, armed personnel intently monitor fastidiously delineated borders, looking for to pressure everybody to observe clear guidelines. However at sea, regulation is nearly the alternative. The system that governs worldwide transport is, at its basis, voluntary.
The oceans run on belief
The monitoring of ships is voluntary. The Worldwide Conference for the Security of Life at Sea – signed by 167 nations – requires nearly each industrial vessel to hold a radio transponder that broadcasts the ship’s identification, place, pace and heading to port authorities, coast guards and industrial monitoring networks.
That worldwide settlement, which is enforced by particular person nations, requires ships to go away the transponders on and lively. However there is no such thing as a bodily mechanism stopping a crew from switching it off or broadcasting a false place.
When a vessel turns off its transponder and goes darkish, it doesn’t set off an alarm at some international maritime headquarters. There isn’t a such headquarters. The ship merely disappears from the map. Each map.
Nationwide jurisdiction is a matter of desire, not legislation. Each vessel sails underneath the flag of a nation, and that nation is theoretically answerable for regulating and inspecting it. However in observe, a ship’s registration in a specific nation is a industrial transaction. Many law-abiding transport corporations make this enterprise resolution, however this method leaves a gap for individuals who search to skirt the foundations.
A ship owned by a shell firm within the United Arab Emirates can register underneath the flag of Cameroon, Palau or Liberia, or any nation that will lack the sources or the inducement to conduct actual inspections. Even landlocked Mongolia has a registry of oceangoing ships flying its flag.
When a vessel comes underneath scrutiny from port inspectors or coast guards, it may possibly merely reregister underneath a special flag. Some registries even provide on-line registration. If the brand new registration is fraudulent or the registry doesn’t truly exist, the vessel successfully turns into stateless.
Then there may be insurance coverage, which is the closest factor the maritime system has to an actual enforcement mechanism. Mainstream insurers, largely primarily based in London, require vessels to fulfill security requirements, carry correct documentation and adjust to worldwide commerce sanctions. A ship with out insurance coverage protection can’t simply enter main ports or safe cargo contracts with respected companies. These restrictions are exactly what froze so many law-abiding ships within the Persian Gulf when conflict broke out.
However corporations can keep away from these guidelines, too. Two-thirds of ships carrying Russian oil – the commerce of which is restricted by the U.S. and different nations – reportedly have “unknown” insurance coverage suppliers, which means no person is aware of whom to name to cowl the cleanup prices after a spill or collision. The enforcement mechanism works till ship homeowners notice they’ll simply choose out of it solely, utilizing much less respected ports or transferring oil from ship to ship out at sea.
What opting out appears like
The outcomes of this voluntary system may be surreal. In December 2025, the US seized a sanctioned tanker known as the Skipper, which was flying the flag of Guyana – though that nation had by no means registered it. The vessel was, in authorized phrases, stateless, crusing underneath the authority of no nation on Earth.
One other vessel, the Arcusat, went additional. Investigative reporting discovered that it had modified its Worldwide Maritime Group identification quantity, a novel seven-digit code assigned completely to each ship. It’s the maritime equal of scraping the VIN off a automotive.
Now layer these strategies collectively. An entity purchases an getting old tanker that will in any other case be scrapped. It registers the ship by means of a shell firm, pays for a flag of comfort, carries opaque insurance coverage and switches off its transponder when approaching delicate waters.
It hundreds sanctioned oil by means of a ship-to-ship switch on the open ocean and delivers its cargo to a purchaser who asks no questions. If the vessel attracts consideration, it modifications its identify, reregisters underneath a special flag and begins over.
In response to maritime intelligence agency Windward, roughly 1,100 darkish fleet vessels have been recognized globally, representing roughly 17% to 18% of all tankers carrying liquid cargo, which is primarily oil.
Why it issues now
The darkish fleet didn’t emerge as a result of the maritime system is damaged. It emerged as a result of the system is constructed on voluntary participation, all theoretically ensured by market forces.
For many years, the system labored not as a result of it pressured compliance however reasonably as a result of opting out was extra pricey than opting in.
What modified is that worldwide sanctions made compliance ruinously costly and politically disastrous for some nations. A system constructed on voluntary participation, it turned out, may very well be voluntarily left.
In case your nationwide financial system will depend on oil exports, and the compliance system is stopping these exports, you construct a parallel system. Iran started doing so in 2018, after sanctions have been reimposed as a part of negotiations over its nuclear improvement. Russia dramatically expanded that system in 2022 as restrictions hit within the wake of its invasion of Ukraine.
Now, with the Strait of Hormuz successfully closed to aboveboard maritime commerce, the one vessels nonetheless transferring are those that ignore the foundations.
However the existence of the darkish fleet doesn’t imply that the foundations of the ocean have failed. Relatively, it reveals what sort of guidelines they all the time have been. Unlawful oil is the one oil transferring in a disaster. In my opinion, that sends a message to these nonetheless taking part in by the foundations: Opting out is perhaps a viable possibility.
The opinions and views expressed are these of the writer alone and don’t essentially characterize these of the Division of the Navy or the U.S. Naval Conflict Faculty.
Charles Edward Gehrke, Deputy Division Director of Wargame Design and Adjudication, US Naval Conflict Faculty
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