Senators from both parties pressed the Pentagon’s top lawyer, Earl Matthews, in a classified briefing to better explain the legal basis for U.S. military strikes on alleged Latin American drug boats.

Matthews cited President Trump’s designation of some cartels as foreign terrorist organizations to justify unilateral action but declined to provide a written rationale.

Lawmakers, including Sen. Tim Kaine and Sen. Jack Reed, expressed concern about the lack of evidence and legal justification, while some Republicans, like Sen. Tom Cotton and Sen. Joni Ernst, defended the strikes.

The administration later declared a “non-international armed conflict” with the cartels and claimed the actions were lawful under U.S. and international law, the Wall Street Journal has reported.

Venezuelan President Nicolás Maduro has threatened a state of emergency in response.