Whether Maduro is a baddie or not, taking military action requires buy-in from the UN Security Council. Specifically: nine affirmative votes from the 15-member council, provided that none of the five permanent members (China, France, Russia, UK, US) cast a veto. And it's only allowed to 'maintain or enforce international peace and security'. The charter contrasts this to building
The US should've consider how their war-plans 'maintain or enforce international peace and security' before commencing. Or even fabricate' sexed up Dossiers' on weapons of mass destruction like when the US invaded Iraq.
Self-defence is the only valid excuse for using arms without prior security council approval and acting without a plan for peace and security.