President Donald Trump sharply increased claims of presidential power in the arena of national security on March 15, 2025, when he invoked the Alien Enemies Act of 1798 to justify new measures targeting the Venezuelan drug-trafficking gang Tren de Aragua (TdA), allegedly an ally of Nicolas Maduro’s government. According to Trump’s proclamation, TdA “is a designated Foreign Terrorist Organization with thousands of members, many of whom have unlawfully infiltrated the United States and are conducting irregular warfare and undertaking hostile actions against the United States.” The organization “has engaged in and continues to engage in mass illegal migration to the United States to further its objectives of harming United States citizens, undermining public safety, and supporting the Maduro regime’s goal of destabilizing democratic nations in the Americas, including the United States.”
Collusion between the Maduro regime and TdA, Trump charged, has produced a “hybrid criminal state” that is “perpetuating an invasion of and predatory incursion into the United States,” posing a substantial danger to the country. The president specifically emphasized the alleged “invasion” as the reason for invoking the Alien Enemies Act. He then stated that all alien enemies described in section 1 of his proclamation “are subject to immediate apprehension, detention and removal” from the United States.
Opponents of the Trump administration immediately denounced the president’s move as unconstitutional and challenged it in court. The rulings so far have been mixed, but the U.S. Supreme Court has at least slowed the administration’s use of AEA’s deportation proceedings on due process grounds, much to the anger of the White House.
Trump’s critics accuse him of trying to implement his hardline views on immigration policy under the false guise of a national security imperative. If Trump’s strategy were allowed to stand, critics contend, undocumented immigrants from Venezuela and other countries could be deported with little or no due process. They would be treated as members of an invading terrorist army. Advocates of a liberal immigration policy consider the invocation of the Alien Enemies Act as a mortal threat to their agenda.
One of their most prominent arguments was that the AEA can be implemented only when the United States is at war. Since no congressional declaration of war was in effect against either TdA or Venezuela, their rationale was that the president could not lawfully invoke and implement the Alien Enemies Act.
Two factors weaken their argument. First, Trump specifically cited an “invasion” as the justification for his action. It has been long settled law that the president can respond to an invasion without waiting for a declaration of war from Congress. At the Constitutional Convention, James Madison had the original phrase “to make War” changed, to afford the president the ability to respond to sudden attacks. Even the constitutional scholars at the liberal Brennan Center implicitly concede that the administration’s insistence that the U.S. is responding to an invasion might complicate criticism of Trump’s actions:
The president may invoke the Alien Enemies Act in times of “declared war” or when a foreign government threatens or undertakes an “invasion” or “predatory incursion” against U.S. territory. The Constitution gives Congress, not the president, the power to declare war, so the president must wait for democratic debate and a congressional vote to invoke the Alien Enemies Act based on a declared war. But the president need not wait for Congress to invoke the law based on a threatened or ongoing invasion or predatory incursion. The president has inherent authority to repel these kinds of sudden attacks — an authority that necessarily implies the discretion to decide when an invasion or predatory incursion is underway.
The position adopted by Trump’s opponents is weakened further because Congress has allowed previous presidents to run amok for decades waging undeclared wars in multiple countries. Congress issued the last official declaration of war in June 1942, against Nazi Germany’s allies Hungary, Romania, and Bulgaria. Yet Washington has attacked numerous countries and political movements since then, resulting in extensive deaths and destruction. Indeed, U.S. administrations have waged lengthy, full-scale wars in such places as Korea, Vietnam, Afghanistan, and Iraq.
Although Congress made a feeble attempt to reclaim some of its constitutional powers regarding war and peace with the passage of the War Powers Resolution in 1973, that change had a meager effect. The authority of Congress to declare war has become little more than an archaic historical curiosity. It is mighty late for Trump’s opponents to take a stand regarding the limits of the president’s war powers. Their choice of the Alien Enemies Act as the proper vehicle for a constitutional challenge is also questionable, since the current administration can make at least a plausible case that it is responding to an invasion of U.S. territory.
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Trump’s position that the United States is effectively at war with TdA, thereby warranting the use of the Alien Enemies Act, virtually begs for a landmark decision from the U.S. Supreme Court. His rationale that the United States is being “invaded” by an organized hostile force seems a stretch, but it is decidedly more credible than the arguments that Trump’s predecessors have used to justify their wars and other “emergency actions.”
One could certainly assert that the terrorist attacks on 9/11 qualified, and a reasonable case could be made that the Libyan government’s role in the bombing of Pan American flight 103 over Lockerbie, Scotland, in 1988 constituted an attack on the United States. But any notion that Washington’s warfare against Muslim forces in Lebanon in 1983, bombing the Bosnian Serbs in 1995, bombing Serbia itself in 1999, or invading and occupying Iraq in 2003 (among Washington’s other undeclared wars) were exercises in national self-defense is preposterous on its face. All of those episodes were wars of choice—indeed, gratuitous wars of aggression.
The Trump administration’s current case, while probably insufficient, is at least more plausible than the justifications for most of the earlier presidential actions. Yet, many of the most vocal critics of Trump’s behavior regarding his invocation of the Alien Enemies Act were silent about those earlier manifestations of the imperial presidency—and remain so. This episode provides an ideal opportunity for the judicial branch to weigh in about the nature and extent of the war powers of both Congress and the presidency. Such a clarification is badly needed.
