The premise

There is a way to think about Iran sanctions that focuses on the headline: "Iran can't sell oil." This is the version you see on cable news. It is also, in almost every particular, wrong.

Iran has been under some form of US sanctions since 1979. It has been under escalating oil sanctions since 2012. Its crude production, at the time of the current strikes, was approximately 3.2 million barrels per day. Its exports — the barrels that actually leave the country — were running around 1.7 million barrels per day, with roughly 90% going to China.^[4]

The sanctions didn't stop the oil from flowing. They changed who ships it, who insures it, who pays for it, and what currency it settles in. This is worth understanding, because the plumbing of sanctions evasion tells you more about the global financial system's actual structure than a decade of policy speeches.

The shadow fleet

Start with the ships.

To move crude oil legally, a tanker needs several things: a flag state registration (the country whose laws it sails under), protection and indemnity insurance (P&I, which covers third-party liability), hull and machinery insurance, and access to ports and ship-to-ship transfer zones. Western sanctions effectively cut Iranian crude out of the legitimate tanker market by making it illegal for Western insurers, flag states, and port operators to handle it.

So Iran built a parallel system. At last count, roughly 285 tankers were operating in what the industry calls the "dark fleet" — vessels that turn off their Automatic Identification System transponders, falsify their cargo documentation, and conduct ship-to-ship transfers in international waters to obscure the origin of the crude.^[2]

The mechanics of how this works, step by step:

1. An Iranian tanker loads crude at Kharg Island.
2. It sails to a rendezvous point — commonly the waters off Oman, Malaysia, or the South China Sea.
3. It transfers its cargo to a second tanker, which has different flag registration and documentation showing the oil as "Malaysian blend" or "Omani crude."
4. The second tanker sails to a Chinese port — usually a Shandong province terminal serving one of the independent "teapot" refineries.
5. Payment is arranged through a network of intermediary companies, typically in yuan, through banks that are either Chinese state-owned or operating in jurisdictions that don't enforce US secondary sanctions.

Each of these steps has its own industry, its own specialists, and its own failure modes. The flag registration problem is illustrative.

The Cameroon question

A tanker needs a flag. Reputable flag states — Panama, Liberia, the Marshall Islands — have largely complied with sanctions pressure and deregistered vessels suspected of carrying Iranian oil. So the dark fleet started shopping for flags that wouldn't ask questions.

Cameroon emerged as the registry of choice. As of early 2026, approximately 13% of the identified dark fleet sailed under the Cameroonian flag.^[3] Cameroon is not a traditional maritime nation. It has no significant domestic shipping industry. Its flag registry is, by most accounts, operated by a private company under license from the Cameroonian government.

The incentive ladder is clean:

1. Cameroon's flag registry generates revenue — modest by global standards, significant for the ministry that controls it.
2. The ships need a flag, any flag, and they'll pay a premium for one that doesn't conduct due diligence.
3. The US Treasury could sanction Cameroon's registry, but doing so would be diplomatically awkward and operationally trivial — the fleet would simply reflag to Palau, or Gabon, or whoever is next in the queue.
4. So the dark fleet rotates through compliant flag states the way a browser rotates through proxy servers.
5. The sanctions enforcement apparatus plays whack-a-mole. The moles are winning.

This isn't a failure of sanctions design. It's a structural feature: any system that relies on voluntary compliance by 190+ sovereign states will find its weakest link, and the weakest link will be whoever has the least to lose from noncompliance.

The payment rails

The oil gets to China. How does Iran get paid?

Not in dollars. Iran has been largely disconnected from the SWIFT messaging system and the dollar-denominated correspondent banking network since 2018. What remains is a patchwork of alternative settlement mechanisms, none of which are efficient and all of which extract significant rents from Iran.

The primary channel is yuan settlement. Chinese refiners — particularly the independent teapots in Shandong — pay for Iranian crude in renminbi, through Chinese banks that have no meaningful US exposure and therefore limited vulnerability to secondary sanctions. The payment often passes through three or four intermediary entities, each taking a cut, before reaching an account that the Iranian government can access.^[10]

In February 2026, FinCEN identified a shadow banking network that had moved approximately $9 billion in Iranian oil revenues through a chain of front companies spanning the UAE, Turkey, and Hong Kong.^[1] The network used a technique called "nesting" — creating accounts within accounts at correspondent banks, layering transactions through shell companies with no apparent business purpose other than moving money from point A to point B while making the path untraceable.

This is expensive. Estimates vary, but the sanctions evasion tax — the spread between what Iranian crude would fetch in a transparent market and what Iran actually receives after intermediaries, currency conversion, and risk premiums — is probably 15-25% of the notional value. On 1.7 million barrels per day at, say, $70 per barrel, that's roughly $18-30 million per day in value that evaporates into the evasion infrastructure.

Iran gets paid. But it gets paid at a discount, in a currency it can't fully convert, through channels it doesn't fully control.

The domestic consequences

What does the rial look like when this is your payment system?

The rial crossed 1,000,000 to the dollar in the open market in early March 2026 — a psychologically significant threshold, even if the actual exchange rate had been deteriorating for months. The official rate, maintained by the Central Bank of Iran for approved imports, was roughly 285,000 to the dollar. The gap between the official and market rates — the "parallel market premium" — was running at approximately 250%.^[6]

Inflation was officially 43.3%, though independent estimates put the real figure higher.^[9] Food prices in particular had been rising faster than the headline number, driven by the cost of importing wheat, cooking oil, and animal feed through the same sanctions-constrained channels.

The mechanism by which sanctions become domestic economic pain is not complicated, but it is worth drawing:

1. Iran sells oil at a discount because the evasion infrastructure extracts rents.
2. It receives yuan, not dollars, which limits what it can buy and where.
3. The Central Bank defends the official rate by restricting dollar access to "essential" imports, creating a parallel market for everything else.
4. The parallel market rate reflects the true scarcity of foreign exchange.
5. Importers who can't access the official rate pass their higher costs to consumers.
6. Consumer prices rise. Wages don't — not at the same pace.
7. The government subsidizes fuel and bread, which absorbs fiscal capacity that could go elsewhere.
8. The fiscal squeeze gets funded by printing rials, which pushes the parallel rate down further.

This is a textbook inflationary spiral with a sanctions-specific accelerant: the more effective the evasion infrastructure becomes at routing around financial restrictions, the more rent-seeking intermediaries take, and the less of the actual oil revenue reaches the Iranian treasury.

Operation Southern Spear

The US Navy's contribution to the sanctions enforcement picture has been Operation Southern Spear — a series of interdictions targeting dark fleet tankers in the Arabian Sea and the Gulf of Oman.^[7]

The operational concept is straightforward: intercept tankers carrying undocumented crude, seize the cargo, and either divert the vessel to a cooperating port or force a ship-to-ship transfer onto a US-controlled tanker. The seized oil is eventually sold, with proceeds going to a US government account.

The legal basis is a combination of executive orders, IEEPA authorities, and forfeiture proceedings. The practical basis is that the US Fifth Fleet has the most capable surface combatants in the region and the dark fleet, by definition, doesn't have naval escorts.

But the interdictions are a rounding error on total Iranian exports. The Navy can intercept a handful of tankers per month. Iran is exporting on roughly 50-60 tanker loads per month. The math doesn't close, and it isn't designed to. The interdictions are partly operational, partly signaling: "We know what you're doing, and we can impose costs whenever we choose to."

The question is whether those costs change behavior. For the Chinese teapot refiners — who buy Iranian crude precisely because it's cheap — the answer has generally been no, at least until the Treasury designates a specific entity that their banks actually care about.^[8]

The China variable

And this is where the entire sanctions architecture meets its structural limit.

China buys approximately 90% of Iran's exported oil.^[5] If China stopped buying, Iran's oil revenue would collapse overnight. The sanctions would, in effect, work. The US knows this. China knows this. Iran knows this.

China doesn't stop buying because:

1. Iranian crude is cheap — discounted $5-10 per barrel below comparable grades.
2. It provides supply diversification away from Saudi Arabia and Russia (ironically, both US partners in different contexts).
3. It gives Beijing leverage over Tehran — the implicit message being: "We're your lifeline, so listen to us on [pick your topic]."
4. Enforcing US sanctions against Chinese companies buying Iranian oil would trigger a secondary sanctions war that Washington has, so far, been unwilling to fully escalate.

The result is a stable equilibrium in which the sanctions are enforced enough to impose real costs on Iran (the evasion tax, the currency collapse, the inflation) but not enforced enough to actually cut off the revenue (because that would require sanctioning Chinese banks, which would require a different kind of confrontation).

One way to read this: the sanctions are working as intended — degrading Iran's fiscal capacity without provoking a Chinese confrontation. Another way: the sanctions are a performance of enforcement that enriches intermediaries, impoverishes Iranian citizens, and leaves the regime's core revenue stream intact. A third way: both are true simultaneously, and the ambiguity is the policy.

In any case, Iran's oil still flows. The ships are older, the flags are stranger, the payment rails are more circuitous, and the Iranian consumer pays the spread. But the barrels get to Shandong.

Straightforward.

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Things happen

The dark fleet's average vessel age is 18 years, versus 10 for the legitimate tanker fleet. Cameroon's maritime registry was briefly suspended by the International Maritime Organization in 2024, then reinstated. Iran's gasoline imports — distinct from crude exports — have increased 40% since 2023 because domestic refining capacity can't meet demand. Turkey has become a secondary sanctions evasion hub, with Istanbul-based trading houses handling an estimated $3-5 billion in Iranian-origin transactions annually. The rial has lost 98% of its value against the dollar since 2018. China's Shandong province has 40+ independent refineries, collectively processing about 2.5 million barrels per day. OFAC has designated over 400 entities connected to Iranian oil since 2022. The average ship-to-ship transfer takes 24-36 hours.