Donald Trump’s executive order renaming the Department of Defence as the Department of War is a perfect encapsulation of how he employs the military. It is gimmicky and newsworthy, it prioritises style over substance — and pushes the legal limits of presidential power.

The “Department of Defence” was named by Congress in 1949, so it cannot be changed by executive order. Trump’s directive portrayed the change as a “secondary title” for the Department of Defence and urged Congress to make the change official, but defence secretary Pete Hegseth isn’t waiting for legislative authorisation to rebrand himself as the “Secretary of War”. The switch in 1949 was not made because the armed forces went “wokey” and stopped winning wars, as Trump alleged. The old Department of War had been solely in charge of the Army. The new name was for an expanded agency that also included the Navy, Marine Corps and Air Force.

But while renaming the defence department is pointless and wasteful — new signage could cost millions of dollars — it is not nearly as troubling as the uses to which Trump puts the military. The President is employing the armed forces ostensibly to fight crime at home and drug smuggling abroad. In the process, however, he is pushing military personnel into dangerous and uncharted legal waters — and, ironically, moving them farther away from fighting actual wars.

Last week, the administration announced that the US military had blown up a speedboat in the Caribbean allegedly full of Venezuelan Tren de Aragua gang members smuggling drugs. All 11 people on board died. Interdictions of suspected drug smugglers are nothing new. But simply blowing up a boat is unprecedented. Normally, the Navy or Coast Guard seize the vessel and arrest the crew.

Secretary of State Marco Rubio said that kinetic strike was done on Trump’s orders, because “the President has a right to eliminate immediate threats to the United States”. But it is not clear how a speedboat in the Caribbean, even one full of drugs, constituted “an immediate threat”, especially when Rubio initially said that its destination was Trinidad.

The strike is a troubling new chapter in a trend that began in 2001, and continued through Republican and Democratic administrations, with the United States employing missile and drone strikes to kill suspected terrorists without benefit of trial. The administration is piggybacking on that history by designating Tren de Aragua as a foreign terrorist organisation. But calling it a terrorist group does not automatically give the President the power to kill its purported members.

Past administrations justified lethal strikes by citing the 2001 Authorisation for the Use of Military Force against al-Qaeda and its supporters and a similar 2002 authorisation against Iraq, along with the military’s inherent right of self-defence when attacked. But Tren de Aragua has nothing to do with al-Qaeda, and comparing its criminality to a terrorist attack on the US is a stretch. Trump has argued that Tren de Aragua is engaged in hostilities against America at the behest of the Venezuelan regime, but the US intelligence community has undercut that claim.

Even while assembling a formidable armada in the waters near Venezuela, Trump has not asked Congress for an authorisation for the use of force against Tren de Aragua or any other drug cartel. The President, who has long advocated the death penalty for drug dealers, simply told the military to go out and act.

Experts in the laws of armed conflict raise serious concerns about the legality of the US strike. Ryan Goodman, who was a special counsel at the defence department during the Obama Administration, wrote on Bluesky: “I literally cannot imagine lawyers coming up with a legal basis for lethal strike of suspected Venezuelan drug boat.”

Matthew Waxman, who served in senior national security positions in the George W. Bush administration, told me: “The President can label this like the war against al-Qaeda, but that doesn’t make it legally so. This is yet another astonishing theory of Trump’s powers; this one being used to justify murky operations that likely violate international law and perhaps domestic law, too.”

This would hardly be the first use of military force in which the administration has been found in violation of the law. US District Judge Charles R. Breyer ruled last week that, by dispatching National Guard troops to Los Angeles this summer, Trump violated the 1878 Posse Comitatus Act, which forbids the use of the military in domestic law enforcement. (The judge’s order has been stayed pending appeal.) The justification for the deployment was the claim that the troops were needed, the judge wrote, “to quell a rebellion and ensure that federal immigration law was enforced”, but, he concluded, “There was no rebellion, nor was civilian law enforcement unable to respond to the protests and enforce the law.”

Aside from issues of legality, there is the issue of strategy: it is far from clear how presumably temporary troop deployments will make a significant dent either in crime across the country or in the multibillion-dollar industry of smuggling drugs into America. US troops are highly unlikely to be able to significantly reduce smuggling operations, to say nothing of most domestic crime, and the cost of attempting to do so will be high. (The National Guard deployment to Washington is estimated to cost $1 million a day.) If the administration has a coherent strategy, it is not being shared with the public or Congress.

Trump’s deployments are showy gestures that detract from the armed forces’ primary, war-fighting mission and put them on a perilous path of engaging in potentially illegal actions. No wonder Hegseth began his tenure by firing senior judge advocates-general, ie, the military’s lawyers. Legality in the use of force appears of little interest to the administration.

Senior officials, indeed, seem to revel in their contempt for the rule of the law. Hegseth said on Friday that the “War Department” would be concerned with “maximum lethality, not tepid legality”. On Saturday, JD Vance, posting on X, called the strike on the alleged drug-smuggling boat “the highest and best use of our military”. When an online critic argued that “killing the citizens of another nation who are civilians without any due process is called a war crime,” the Vice-President replied: “I don’t give a s*** what you call it.”

• Max Boot is a Washington Post columnist and a senior fellow at the Council on Foreign Relations. A Pulitzer Prize finalist in biography, he is the author, most recently, of The New York Times bestseller Reagan: His Life and Legend, which was named one of the ten best books of 2024