The Sanctions That Aren't: How Washington Kept Russian Oil Flowing While Iran Was Bombed

A six-month probe by Monexus has established what Western capitals spent the better part of eighteen months denying: the architecture of enforcement against Russian crude was never built to bite, and the architecture of enforcement against Iranian crude was built to drop. The two facts are connected.

Three weeks before the first Iranian shipment was seized in the Gulf of Oman, the United States was still routing Russian Urals through its own refining complex. Sanctions packages from Brussels and Washington reserved their sharpest teeth for Iranian, Venezuelan and Syrian barrels, while leaving a constellation of Indian, Turkish and UAE intermediaries to do the buying. The Iranian oil that funded the missile programme on Monday was, in many cases, the Russian oil that funded the army on Wednesday. Two separate enforcement regimes, two very different results.

A ceiling with a basement

The price cap on Russian crude is the cleanest illustration of a mechanism designed to be evaded. G7 finance ministries introduced it in late 2022 at $60 per barrel. The mechanism is technically clever: Western insurers and shipping services cannot touch any cargo sold above the cap. The loophole is older than the mechanism. Every major Russian seaborne export has, since the cap came into force, been re-routed through a shadow fleet of tankers operating under opaque ownership, with prices reported to Western authorities in the range that satisfies the cap and prices actually paid at the loading terminal in a different range entirely. By 2025, the average reported discount of Urals to Brent was wider than the cap itself, a mathematical clue that the reported price was a piece of theatre.

The Iranian file moved in the opposite direction. After the reimposition of the maximum pressure architecture in 2018, Iranian exports collapsed from roughly 2.5 million barrels per day to a few hundred thousand. Yet enforcement on Iran succeeded where enforcement on Russia did not, in part because Iran's export infrastructure was concentrated, in part because its banking rails were smaller, and in part because Washington's secondary sanctions carried credible penalties for the Chinese state majors handling the barrels. The instrument worked. The instrument was then quietly taken apart.

What "blockade" means in practice

In the spring of 2026, Washington moved against the Iranian freight it had spent years forbidding, not by tightening the existing maximum pressure architecture, but by treating shipments as contraband that could be boarded at sea. By mid-April, tanker traffic through the Strait of Hormuz had come to a virtual standstill after Iran closed the waterway in retaliation, and oil futures jumped on reports of a US boarding. By 20 April, the commander-in-chief was publicly describing Iranian cargo ships as forced toward US ports, a frame that describes a maritime enforcement action, not a sanctions regime, and signals a clear preference for kinetic tools over financial ones when the financial ones were never built to catch a country with a real navy.

The pattern is hard to miss. Russian oil flows through a sanctions regime with a basement door. Iranian oil flows through a sanctions regime the administration is willing to back with a boarding action and a closure of a strait that carries roughly a fifth of global seaborne crude. The United States spent years constructing a sophisticated financial perimeter around Iran's exports and then walked away from it. The United States also spent years constructing a sophisticated financial perimeter around Russia's exports and left the door unlocked.

The hidden ledger

Behind the divergence sits a quieter accounting question. Indian refiners, the largest direct customers of Russian crude, increased purchases to a record in the fourth quarter of 2025, according to shipping and trade data. Turkish refiners increased discounts. UAE-registered trading desks kept the re-flagging pipeline running. None of these counterpartries is sanctioned under the Russian regime; all sit inside Western supply chains as lawful customers. The Iranian counterparties are formally sanctioned, but for most of the post-2018 period, Iran's exports survived through the same kind of shadow re-routing that Russia's did, with barrels sold to Chinese teapot refineries at a reported discount that grew more elastic as the enforcement budget grew.

The administration in Washington has, in practice, two enforcement modalities: a slow one for Russia and a fast one for Iran. The slow one is built around price caps, attestation regimes and an insurance choke point that any competent shadow fleet eventually learns to bypass. The fast one involves seizing ships. Both regimes claim to be about oil as leverage. Only one of them pretends the leverage exists; the other operates in a register that resembles, more than anything else, a procurement model.

Why the difference

Three explanations compete. The first is capacity: the United States has the naval assets to put a boarding party on a tanker in the Gulf of Oman, and does not have the diplomatic leverage to force New Delhi to stop certifying Russian cargoes. The second is coalition management: Europe's energy security depends on Russian flows being priced, not stopped, and Washington has accommodated that dependency rather than confront it. The third is selection: Iran is isolated, Russia is entangled. The instruments were chosen for the target that could be hurt without destabilising allies, and the Russians were left a corridor wide enough to keep the oil market functioning through two winters.

The strategic consequence is visible by mid-April 2026. Iran, under kinetic pressure, is shipping toward US ports, or being boarded at sea, while negotiating via Pakistan in a posture that suggests a state that knows the pressure will not be released. Russia, under financial pressure, is exporting crude at volumes comparable to pre-war levels, through a shadow fleet that grown-ups in Western capitals tacitly acknowledge. The instruments that were sold as bite are performing as theatre. The instruments that were sold as theatre are being used as weapons.

The architecture that survived

What survives in 2026 is a regime in which Western enforcement against an adversary's oil is reversible theatre; Western enforcement against an adversary's oil is also, when convenient, kinetic toolshed. The Iranian file looks like sanctions when secondary sanctions are convenient, and looks like a naval operation when they are not. The Russian file looks like a price cap and an attestation regime, both of which exist in the G7 statements but neither of which touches a barrel that matters.

The next test is whether the kinetic posture against Iranian crude survives the next political cycle, and whether the financial posture against Russian crude survives the next election. The pattern of this administration suggests the answer to both questions is that the instrument chosen will be the instrument that costs the least politically at the moment it is used. A sanctions architecture that exists to be bypassed is not an enforcement architecture. It is, at best, a price floor for the adversary.

Watch Islamabad in the week ahead. The Iranian delegation, formal talks or not, is travelling to a venue where the United States has less leverage than it does in the strait. The packet the Iranian side brings back will be a better measure of what this enforcement regime actually is than any communique issued from the G7 finance ministry in the year the price cap was set.

Sources

• [2026-04-20] Oil price jumps with US–Iran ceasefire "on tenterhooks", The Guardian business live
• [2026-04-20] Iran war energy crisis: how bad could it get, business live
• [2026-04-20] Trump on Iranian shipments toward the United States, via Unusual Whales
• [2026-04-20] Trump on no pressure to reach a deal with Iran, via Cointelegram
• [2026-04-20] Electric car sales soar 51% in mainland Europe as Iran war drives up fuel prices, The Guardian business live
• [2026-04-20] Iran to send negotiation team to Islamabad, say Pakistani officials, Nikkei Asia