31 CFR § 515.550 - Certain vessel transactions authorized.
(a) Unless a vessel is otherwise engaging or has otherwise engaged in transactions that would prohibit entry pursuant to § 515.207, § 515.207 shall not apply to a vessel that is:
(1) Engaging or has engaged in trade with Cuba authorized pursuant to this part;
The authorization in this paragraph includes, for example, trade with Cuba authorized pursuant to § 515.533, § 515.559, or § 515.582, or by specific license.
(2) Engaging or has engaged in trade with Cuba that is exempt from the prohibitions of this part (see § 515.206);
(3) Engaging or has engaged in the exportation or reexportation to Cuba from a third country of agricultural commodities, medicine, or medical devices that, were they subject to the Export Administration Regulations (15 CFR parts 730 through 774) (EAR), would be designated as EAR99;
(4) A foreign vessel that has entered a port or place in Cuba while carrying students, faculty, and staff that are authorized to travel to Cuba pursuant to § 515.565(a); or
(5) Carrying or has carried persons between the United States and Cuba or within Cuba pursuant to the authorization in § 515.572(a)(2) or, in the case of a vessel used solely for personal travel (and not transporting passengers), pursuant to a license or other authorization issued by the Department of Commerce for the exportation or reexportation of the vessel to Cuba.
(b) Unless a vessel is otherwise engaging or has otherwise engaged in transactions that would prohibit entry pursuant to § 515.207, § 515.207(a) shall not apply to a foreign vessel that has engaged in the exportation to Cuba from a third country only of items that, were they subject to the EAR, would be designated as EAR99 or would be controlled on the Commerce Control List only for anti-terrorism reasons.