That strike followed the killing of 11 people aboard another boat in the Caribbean earlier this month, which US officials later acknowledged had turned back toward Venezuela before the US carried out the strike—further calling into question the claim that the vessel was headed toward the US and posed a threat.
"President Trump has no legal authority to launch strikes or use military force in the Caribbean or elsewhere in the Western Hemisphere," said Kaine in a statement, adding that the administration has refused to release basic information showing it was necessary to attack the vessels.
The strikes have been condemned by legal and human rights experts as "murder" and "extrajudicial executions" of civilians—people who, if they were in fact bringing drugs to the US as the White House has claimed, would typically be confronted by law enforcement agencies instead of struck by the military.
The US Coast Guard has in the past intercepted boats and searched them to confirm suspected drug smuggling, and arrested their crews.
As Sen. Chris Murphy (D-Conn.) said last week, Trump's claim that boats are carrying fentanyl, which caused roughly 48,000 drug overdoses in the US last year, is likely inaccurate. Fentanyl is primarily trafficked from Mexico and Central America into the US, he noted, not from Venezuela.
Secretary of State Marco Rubio said earlier this month that the United Nations Office on Drugs and Crime's assessment that Venezuela is also not a major source of cocaine was of no importance to the administration.
"I don’t care what the UN says," Rubio told reporters after the first military strike in the Caribbean.
The White House has not released evidence showing that the boats were carrying drugs; after the first bombing, the president said the administration had "tapes of [the victims] speaking" that showed they were members of the Venezuelan gang Tren de Aragua, which it has designated a terrorist organization that works directly with the South American country's government—despite US intelligence agencies' finding that the group does not work with President Nicolás Maduro.
Even if the president's suspicions were correct, said Sarah Yager, Washington director at Human Rights Watch, "US officials cannot summarily kill people they accuse of smuggling drugs."
“The problem of narcotics entering the United States is not an armed conflict, and US officials cannot circumvent their human rights obligations by pretending otherwise," Yager said Thursday.
While claiming the military is targeting drug traffickers, Vice President JD Vance suggested this week that the US could mistakenly kill civilians who are not involved in drug activity, joking, "I wouldn't go fishing right now in that area of the world."
The administration has not disclosed a legal analysis of why it believes the strikes, which it has said will continue, are lawful.
Congress has not authorized any military conflict with drug cartels, and at a Senate Armed Services Committee hearing on Thursday, a nominee for a position at the Pentagon was unable to answer Democratic lawmakers' questions about the legality of the administration's strikes.
On Friday, reporting by The New York Times suggested that Republican lawmakers and the White House are working to grant the administration the legal authority to continue the strikes.
A draft bill is circulating around the White House and Congress to grant the president the power to order military strikes to carry out "the drug trafficking war."
The authority would last for five years, and longer if renewed by Congress, and would cover groups that the administration has designated terrorist organizations as well as nations that harbor those groups.
Jack Goldsmith, a former George W. Bush administration official and a Harvard Law School professor, told the Times that the legislation is "insanely broad."
"This is an open-ended war authorization against an untold number of countries, organizations, and persons that the president could deem within its scope," said Goldsmith.
Introducing their resolution on Friday, Kaine and Schiff said they do not want to prevent the US from carrying out strikes in self-defense against an "armed attack."
But, they emphasized, “the trafficking of illegal drugs does not itself constitute such an armed attack or threat.”
Yager called on Congress to also "open a prompt and transparent investigation into the decision-making process behind these attacks, including the legal rationale and chain of command.”
“The US military should immediately halt any plans for future unlawful strikes," she said, "and ensure that all military operations comply with international human rights and humanitarian law."
