Sanctions Screening
Checking customers, counterparties, and blockchain addresses against government lists of parties that firms are forbidden to deal with.
Sanctions are absolute prohibitions rather than risk-based judgments: dealing with a designated party is unlawful regardless of intent or size. Firms screen at onboarding and again on each transaction, matching names, entities, jurisdictions, and, in digital assets, specific wallet addresses. The United States Office of Foreign Assets Control has included digital currency addresses in its Specially Designated Nationals list since 2018, and designations have at times covered software-based mixing services as well as individuals. Some exchanges, block builders, and protocol front ends apply screening to transactions, which is where compliance intersects with debates about censorship resistance.
In practice
Designated addresses appear in the Specially Designated Nationals list alongside names and passport numbers, and regulated firms must block rather than merely refuse related transfers.
The common misunderstanding
That sanctions apply only to named people and companies, when specific blockchain addresses and deployed software have themselves been designated, and dealings with them are prohibited regardless of who is operating them.