Lethal force against a civilian vessel in international waters is a war crime if not in self-defense. If not in self-defense, only non-lethal actions, such as warning shots or disabling fire, are allowed.
"Not yielding to pursuers" or "suspected of carrying drugs" doesn't carry a death sentence.
The US military "conducted a lethal strike" against an alleged "drug vessel" in the southern Caribbean, Secretary of State Marco Rubio said.
US military ‘conducted a lethal strike’ on alleged ‘drug vessel’ in southern Caribbean, Rubio says | CNN Politics
The United States “conducted a lethal strike” against an alleged “drug vessel” in the southern Caribbean, Secretary of State Marco Rubio said Tuesday.