Critics of the Trump administration say that U.S. strikes on drug-smuggling vessels in the Caribbean, which have thus far destroyed 23 boats and killed 87 people, violate international law. They also claim the military isn’t needed since traffickers found in international waters were previously captured by the Coast Guard and prosecuted in federal courts.

It’s true that prosecutions of foreigners on the high seas have become a mainstay of federal antinarcotics efforts under an obscure 1986 U.S. law known as the Maritime Drug Law Enforcement Act. But MDLEA prosecutions aren’t a legally innocuous alternative to military operations. They are a dubious one, whose constitutional basis in recent years has been questioned by federal judges.

The MDLEA extends U.S. narcotics laws to foreigners on non-American vessels on the high seas, where criminal enforcement is traditionally reserved to the home country. Congress can certainly criminalize smuggling directed at our shores. What makes the MDLEA unique is that it extends jurisdiction to foreign vessels without requiring proof of any connection to the U.S. There have been cases in which the vessels were manifestly bound for other countries.

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The statute treats vessels as “subject to the jurisdiction of the United States” if they are “deemed stateless.” This can mean simply that the home state doesn’t immediately pick up the phone or affirm their nationality, which happens often with small boats. As a result, foreigners captured in international waters can be prosecuted under U.S. law and spend the rest of their lives in a U.S. prison.

Punishing foreign crimes with no U.S. nexus raises serious concerns about the limits on Congress’s powers. The Constitution contemplates Congress having limited law-enforcement powers and even specifies crimes it can punish: treason, counterfeiting, “offences against the law of nations” and “piracies and felonies on the high seas.” Under the last, Congress enacted the MDLEA.

But there is good reason to believe the Felonies Clause doesn’t give Congress the power to punish purely foreign conduct. For one, the Constitution established Congress as part of a government of limited powers within the U.S. Congress certainly doesn’t have broader legislative powers outside the U.S. than it does domestically.

The constitutional phrase “piracies and felonies” hints at the limits on Congress’s power. Piracy is always a species of high-seas felony, making it apparently unnecessary to single out. But piracy was unique in that it could be punished without regard to nationality under what modern international law calls “universal jurisdiction.” By specifically mentioning “piracies” as distinct from other maritime “felonies,” the framers made clear that only the former could be punished universally.

As early as 1799, then-Rep. John Marshall said the U.S. has “no jurisdiction over offences committed on board a foreign ship against a foreign nation.” It would be absurd, the future chief justice argued, for the U.S. to prosecute most crimes by foreigners on foreign ships.

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Prosecuting other maritime crimes, however, requires an explicit source of congressional authority. The Supreme Court said as much in U.S. v. Furlong (1820), which held that punishing crimes other than piracy on foreign vessels fell outside the “acknowledged reach of the punishing power of Congress.” To be sure, the vast expansion of the interstate commerce power since the New Deal has also resulted in an increase in the number of federal crimes. But drug trafficking, if lacking a link to the U.S., is neither commerce “among” the states nor “with” a foreign state.

MDLEA prosecutions went unquestioned by federal judges for a while, but that has changed. A panel of the First U.S. Circuit Court of Appeals held in 2022 that “the prosecution of foreign nationals traveling on such a vessel for a violation of U.S. law is impermissible under the Felonies Clause of the Constitution.” That decision was overturned on procedural grounds by the full court. The Supreme Court has never addressed the issue, leaving a constitutional cloud over such MDLEA prosecutions.

Combating drug trafficking is a legitimate goal. But prosecuting foreign criminality in U.S. courts gives Congress a jurisdictional carte blanche that would wholly undermine federalism if applied domestically. The Supreme Court’s federalism revival in the 1990s began by insisting that federal criminal powers must stem from a clear constitutional grant of legislative authority.

The strikes on narco-trafficking vessels on the high seas raise novel questions of international law, but the exercise of force against foreign foes, including smugglers, is already part of the president’s power, regardless of what international law says about them. In short, domestic prosecutions under MDLEA do violence to the Constitution in ways that extraterritorial violence does not. And given the increasing judicial skepticism of MDLEA prosecutions, it would not be wise to rely on arrest and prosecution to prevent drugs from reaching our shores.