Where a restriction attaches to the origin of goods rather than to a named party, the control depends entirely on origin being determinable. Blending attacks that directly: the commodity is physically mixed with, or documented as, product from an unrestricted source, and the resulting cargo has no origin that can be established from the cargo itself.
It applies wherever a commodity is fungible — crude oil, refined products, grain, metals, coal — because fungibility is precisely the property that makes origin a documentary question rather than a physical one.
How it works
The physical step is straightforward and is a routine commercial operation in other contexts. Cargo from two or more sources is combined, at sea during a ship-to-ship transfer, in a shore tank, in a bonded storage facility, or in a free zone. What comes out is a single parcel.
The documentary step is what matters. The blended cargo is issued with paperwork describing it as originating in the unrestricted source, or in the country where the blending took place, on the basis that processing there conferred a new origin.
Rules of origin determine when processing in a country is sufficient to confer that country’s origin, and the thresholds vary between trade agreements. Genuine substantial transformation confers origin; decanting a cargo from one tank into another does not. Where the claimed processing is minimal, the origin claim is false even though the physical mixing is real.
The tanker case
The best-documented version involves crude and refined products, because the commodity is liquid, the transfers happen at sea, and the analysis is well developed. Cargo is loaded at a restricted origin, transferred to a second vessel at anchorage, blended with cargo of a different provenance, and delivered with documents showing the blend’s stated origin.
The 2020 global advisory issued by State, Treasury and the Coast Guard does not describe the physical blending itself. What it names is the documentary half: it lists falsifying cargo and vessel documents1 as a deceptive practice, and records that evaders have falsified shipping documentation for petrochemicals, petroleum, metals or sand in order to disguise their origin2 . The 2023 price cap advisory supplies the operation that makes it possible, noting that ship-to-ship transfers can be used to conceal the origin or destination of cargo3 .
The distinction matters. Mixing two parcels in a tank is not itself an offence anywhere. What the advisories document is the paperwork that follows it.
The capacity test
The strongest analytical check on an origin claim is production capacity. A country that certifies exports of a commodity in volumes exceeding what it can produce, extract or plausibly re-export is making claims its own economy contradicts. The reasoning can be applied to public data without access to any individual cargo, which is why it recurs in the enforcement record — the Adani settlement turned in part on a load port that had no facility for exporting the product the cargo was said to have loaded there.
How it is caught
Capacity reconciliation. Declared exports against national production, applied at country level, over time. This is the method that scales.
Chemical assay. Crude oils have distinguishable compositional signatures, and testing can indicate provenance. Blending degrades this but does not always defeat it, and cargo samples are routinely retained at loading and discharge.
Voyage reconstruction. An origin claim implies a voyage. Where the vessel’s movements do not support the claimed loading port, or show an unexplained transfer en route, the documents and the track are in conflict. The vessel-level data behind that reconstruction is outside the scope of this site.
Documentary sequence. FATF and the Egmont Group flag trade or customs documents that are missing, appear to be counterfeit, contain false or misleading information, or are frequently modified or amended4 . In practice that is often the first visible sign.