A strike carried out by US forces on a boat in the Caribbean Sea – which the White House says killed 11 drug traffickers – may have violated international human rights and maritime law, legal experts have told BBC Verify.

President Donald Trump announced on Tuesday that US forces destroyed a vessel which he said had departed from Venezuela. He said the boat was operated by the Tren de Aragua cartel and was carrying drugs bound for the US.

US defence officials have so far declined to offer details on the strike, footage of which Trump shared on Truth Social, including what legal authority they relied upon to justify it.

BBC Verify reached out to a range of experts in international and maritime law, with several saying that US may have acted illegally in attacking the vessel.

The US is not a signatory to United Nations Convention on the Law of the Sea, but the US military’s legal advisors have previously said that the US should “act in a manner consistent with its provisions”.

Under the convention, countries agree not to interfere with vessels operating in international waters. There are limited exceptions to this which allow a state to seize a ship, such as a “hot pursuit” where a vessel is chased from a country’s waters into the high seas.

“Force can be used to stop a boat but generally this should be non-lethal measures,” Prof Luke Moffett of Queens University Belfast said.

But he added that the use of aggressive tactics must be “reasonable and necessary in self-defence where there is immediate threat of serious injury or loss of life to enforcement officials”, noting that the US moves were likely “unlawful under the law of the sea”.

Experts have also questioned whether the killing of the alleged members of the Tren de Aragua cartel could contravene international law on the use of force.

Under Article 2(4) of the UN charter, countries can resort to force when under attack and deploying their military in self-defence. Trump has previously accused the Tren de Aragua cartel of conducting irregular warfare against the US, and the state department has designated the group as a Foreign Terrorist Organisation.

But Prof Michael Becker of Trinity College Dublin told BBC Verify that the US actions “stretches the meaning of the term beyond its breaking point”.

“The fact that US officials describe the individuals killed by the US strike as narco-terrorists does not transform them into lawful military targets,” he said. “The US is not engaged in an armed conflict with Venezuela or the Tren de Aragua criminal organization.”

“Not only does the strike appear to have violated the prohibition on the use of force, it also runs afoul of the right to life under international human rights law.”

Prof Moffett said that the use of force in this case could amount to an “extrajudicial arbitrary killing” and “a fundamental violation of human rights”.

“Labelling everyone a terrorist does not make them a lawful target and enables states to side-step international law,” he said.

Notre Dame Law School Professor Mary Ellen O’Connell told BBC Verify that the strike “violated fundamental principles of international law”, adding: “Intentional killing outside armed conflict hostilities is unlawful unless it is to save a life immediately.”

“Sometimes armed groups waging war against governments deal in drugs to pay for their participation in conflict. There is no evidence the gang President Trump targeted is such a group.”

But US officials have been quick to defend the strike. Republican Senator Lindsay Graham wrote on X that the strike was the “ultimate – and most welcome – sign that we have a new sheriff in town”.

His fellow Republican senator, Bernie Moreno from Ohio, wrote: “Sinking this boat saved American lives. To the narco traffickers and the narco dictators, you’ll eventually get the same treatment.”

A White House official told BBC Verify that Trump had authorised the strike on the boat, which they said was crewed by Tren de Aragua members, after it left Venezuela. The official added that the president was committed to using all means to prevent drugs reaching the US.

The Pentagon has declined to share the legal advice it obtained before carrying out the strike.

US Defence Secretary Pete Hegseth told Fox News: “we’ve got incredible assets and they are gathering in the region… those 11 drug traffickers are no longer with us, sending a very clear signal that this is an activity the United States is not going to tolerate in our hemisphere.”

Questions have also been raised as to whether the White House complied with US law in authorising the strike. The US constitution says that only Congress has the power to declare war.

However, Article II – which lays out the president’s powers – says that “the president shall be Commander in Chief of the Army” and some constitutional experts have suggested that this grants the president the power to authorise strikes against military targets. Trump administration sources have previously cited this provision when defending US strikes on Iran.

But it is unclear whether that provision extends to the use of force against non-state actors such as drug cartels.

Rumen Cholakov, an expert in US constiutional law at King’s College London told BBC Verify that since 9/11, US presidents have relied on the 2001 Authorization of Use of Military Force Act (AUMF) when carrying out strikes against groups responsible for the attacks.

“Its scope has been expanded consistently in subsequent administrations,” he added. “It is not immediately obvious that drug cartels such as Tren de Aragua would be within the President’s AUMF powers, but that might be what “narco-terrorists” is hinting at.”

Questions also remain as to whether Trump complied with the War Powers Resolution, which demands that the president “in every possible instance shall consult with Congress before introducing United States Armed Forces into hostilities”.

It is unclear what method the US used to launch the attack. Trump did not offer details in his news conference in the Oval Office and the Department of Defense has failed to offer further information.

In Venezuela President Maduro has yet to respond to the US strikes, but his Communications Minister Freddy Ñáñez has suggested that the footage released by the White House may have been generated using AI. In a post to X, he suggested that water in the video “looks very stylized and unnatural”.

BBC Verify has run the clip through SynthID – Google’s AI detection software – and found no evidence that the footage is fake.

The strikes come amid reports that the US has deployed several naval warships to the region in support of anti-narcotics operations against Venezuela.

We’ve not been able to track all of these vessels. But using information from publicly-available onboard trackers, and videos on social media, we’ve potentially identified four of them in the region.

A ship identifying itself as the USS Lake Erie – a guided missile cruiser – last transmitted its location in the Caribbean Sea on 30 August, east of the Panama Canal on 30 August.

Two others identifying themselves as the USS Gravely and USS Jason Dunham last transmitted their locations in mid-August, at the American base in Guantanamo Bay. A fourth, the USS Fort Lauderdale, transmitted its location north of the Dominican Republic on 28 August.

Trump – who has long sought to oust Venezuela’s President Nicolás Maduro – has authorised a US$50m reward for any information leading to his arrest. The Venezuelan leader claimed victory in last year’s elections, widely viewed as rigged by international observers.

Additional reporting by Lucy Gilder.