On 9 August 2013, several packages of cocaine were found on board a vessel located in international waters. The HMS Lancaster conducted a right-of-visit approach. During this approach, Aybar, who was on board the vessel with the packages, claimed to be a citizen of the Dominican Republic. However, the vessel was determined by law enforcement personnel to be stateless. Aybar was later held in custody by United States law enforcement and convicted for violations of the Maritime Drug Law Enforcement Act (MDLEA).

Aybar filed a motion to dismiss the indictment on the ground that the US Congress lacked the jurisdiction to criminalise his conduct. However, Aybar's motion was denied by the District Court. The District Court reasoned that international law allows the United States to treat stateless vessels as if they were its own. Therefore, people on board stateless vessels navigating on the high seas have effectively waived their rights to object to the exercise of jurisdiction over them by the United States. Aybar appealed.

Held: Appeal dismissed. The majority (Lynch and Barron JJ) confirmed the District Court's reasoning and affirmed Aybar's conviction.

The minority (Torruella J) held that, in accordance with art 110 of the United Nations Convention on the Law of the Sea 1982 (UNCLOS), it is widely accepted that international law confers the right of any nation to approach and 'visit' a vessel if it is suspected that the vessel is stateless. However, the 'right to visit' does not confer jurisdiction on the nation to prosecute the crew members of the stateless vessel under the visiting nation's substantive criminal laws without some nexus between their conduct and the boarding nation. A review of customary international law reveals that art 110 of UNCLOS requires some independent nexus between the visiting state and the suspected basis for the interference. For example, art 110.1.c requires that a nation may only prosecute individuals who engage in unauthorised broadcasting if that nation has an independent basis for asserting jurisdiction over those individuals or that conduct. Otherwise, according to art 89 of UNCLOS, it is a violation of customary international law if a nation applies its domestic law to a stateless vessel's crew members without a nexus or unilaterally extends that nation's sovereignty over the high seas. Since under both UNCLOS and US domestic law, piloting a stateless vessel is not itself in the nature of a universal crime, the US cannot invoke its domestic law, namely MDLEA, to prosecute an individual simply because he is on board a stateless vessel. Thus, Aybar's conviction should be overturned.

[For the subsequent en banc rehearing of this appeal, see United States v Aybar-Ulloa (CMI1175).]