The prompt:

Speak to the following: The Federal Register vs. the OFAC website: which one is legally operative, and what about time gaps between the two?

The response:

The Federal Register is legally operative for OFAC actions that require notice-and-publication; the OFAC website is not a legal instrument.

The distinction turns on the type of action. For designations under most sanctions programs, OFAC’s legal authority to add a party to the SDN List derives from the underlying statute and executive order, and the designation becomes effective when the Director (or Secretary) signs the determination, not when it appears anywhere. OFAC then publishes the SDN List update on its website, typically the same day, and follows with a Federal Register notice, sometimes days or weeks later.

For rules that carry legal force in their own right, the Federal Register is authoritative. Amendments to the sanctions regulations in Title 31 CFR, general licenses that OFAC chooses to codify, and formal rulemakings take legal effect on the date and terms stated in the Federal Register. The Federal Register text is the official version; if the website and the published notice ever diverged, the Federal Register controls.

On the time gaps: the practical answer for compliance purposes is that OFAC treats a designation as effective from the moment of the action, and the SDN List posting on the website is the operational trigger the industry screens against. The Federal Register notice is a legal formality that documents the action and satisfies publication requirements, but the absence of a same-day Federal Register notice does not delay the legal effect of a designation. A party added to the SDN List on Tuesday is blocked as of Tuesday, even if the corresponding Federal Register notice does not run until the following week. The prohibition attaches to the U.S. person’s dealings with blocked property, and OFAC’s position is that the obligation exists once the property interest is blocked, independent of publication timing.

Two nuances worth flagging. First, some due-process and constructive-notice questions have been litigated, and courts have generally accepted that public availability of the SDN List provides adequate notice, which is why the website posting matters practically even though it is not the legal instrument. Second, the effective date stated in a Federal Register notice may differ from the website posting date; where a specific legal deadline or wind-down period runs from an effective date, read that date from the Federal Register text rather than inferring it from when the website was updated.

If you want, I can pull the specific statutory publication requirements (for example, the IEEPA and APA provisions and any program-specific notice language) to tighten the citations.