What is the outcome if a vessel is found without nationality after actions taken under presumptive flag state authority?

When a vessel is found without nationality after actions have been taken under presumptive flag state authority, the correct outcome is that those actions are still deemed permissible. This outcome emphasizes the principle that actions taken under the assumption of a vessel's nationality maintain their validity even if it is later discovered that the vessel lacks formal nationality.

In maritime law, presumptive flag state authority allows enforcement actions against a vessel based on the belief that it is registered to a certain flag state. If it turns out the vessel does not possess nationality, this does not retroactively negate the legitimacy of the actions that were taken while that presumption was held. Thus, enforcement measures remain valid because they were appropriately executed under the information available at the time.

Other options suggest consequences that do not align with this principle. For instance, the nullification of U.S. jurisdiction or requiring immediate release of the vessel would imply a lack of authority in the enforcement actions, which is not consistent with established maritime law practices. Also, invalidating the presumption would conflict with the legal framework that allows for actions based on reasonable assumptions about the vessel's registration status at the time of enforcement.