In 1798, Congress passed the Alien Enemies Act (AEA), which provides that during a state of “declared war,” or when “any invasion or predatory incursion is perpetrated, attempted, or threatened against the territory of the United States by any foreign nation or government,” the President can restrain and remove “all natives, citizens, denizens, or subjects of the hostile nation or government” as “alien enemies.” As the text of the AEA makes explicit, the President can only invoke the AEA’s sweeping authorities under certain circumstances and against certain people.

On March 14th, President Trump invoked the AEA to address what he is calling the “Invasion of the United States by Tren de Aragua,” a criminal cartel with supposed ties to the Venezuelan government. The next day, the administration sent 238 Venezuelan immigrants detained in the United States to a maximum-security prison in El Salvador. It did so without giving any of them their constitutionally mandated day in court. Most of these men have not been heard from since.

A group of Venezuelan citizens detained in Texas challenged their threatened removal to the same notorious foreign prison. In June 2025, CAC filed an amicus brief in the Fifth Circuit supporting their challenge. The brief explains that President Trump’s use of the AEA is unlawful because Tren de Aragua is not a “foreign nation or government” within the meaning of the AEA.

The lawmakers who passed the AEA in 1798 understood the terms “nation” and “government” to be defined by the law of nations, a set of international norms that governed foreign relations between nations at the time. The law of nations set two interrelated qualifications for any entity to be considered a nation or government: self-definition and foreign recognition. The entity had to hold itself as acting on behalf of a group of people living in a defined territory. It also had to be recognized by other nations as speaking on their people’s behalf on the international stage. These were the very qualities that the Founders thought were necessary for the American Revolution to turn thirteen colonies into a new nation.

The AEA’s history underscores why the Act can only be invoked against nations or governments that meet these qualifications. The AEA was passed in response to an ongoing conflict with one “foreign nation or government” in particular—the French Republic. In 1798, the United States was in the midst of a naval conflict, known as the Quasi War, with this erstwhile ally. In response, Congress passed the AEA and its counterpart, the notorious Alien Friends Act. The Alien Friends Act granted the President sweeping power to detain and expel any noncitizen deemed “dangerous to the peace and safety of the United States.” It was immediately attacked as unconstitutional and shortly thereafter allowed to lapse in disgrace.

The AEA, by contrast, was widely considered constitutional. The reason for this disparity was simple: the AEA was understood to be an extension of Congress’s power to declare war. During a state of war, as James Madison explained, Congress had the power “under the law of nations” to hold foreign citizens accountable for the belligerent actions of their home country. But only a nation or government under the law of nations—an entity that claimed the authority to act on its peoples’ behalf and was recognized as having that authority—could demand the sort of allegiance from its people that would justify holding them personally accountable for their sovereign’s actions during war.

This is a high bar. That is why the AEA has been invoked just three times: during the War of 1812, World War I, and World War II. And each time, the United States was in a state of war against an entity that both held itself out and was formally recognized as a sovereign nation or government acting on behalf of the people in its territory.

Tren de Aragua is not a “nation or government” within the meaning of the AEA. Tren de Aragua has never claimed to act on behalf of the inhabitants of a defined territory, and neither the United States nor any other nation has recognized it as having the authority to act on Venezuelans’ behalf. Quite the opposite—on his first day in office, President Trump designated the criminal cartel a “Foreign Terrorist Organization” that threatens the security of both Venezuela and the United States.

The government has argued that courts do not have the authority to second-guess the President’s declaration, but it is emphatically the role of courts to interpret the text of statutes like the AEA and decide whether Tren de Aragua qualifies as a “nation or government” within meaning of that text. It clearly does not.