This is the letter of the law and regulations as they stand, but hopelessly naive as to how actual military command is handled. The military deployed a previously unused weapon on the president’s command without any consultation. This responsibility has been largely delegated from congress to the executive’s discretion (with review) for nearly two decades.

Reminding active service members that their oath is to the constitution, not the executive, at this moment is prudent.

Invading Cuba without Congressional approval would be a clear violation of the Constitution.

But I think it's very dangerous to assume that institutions have the internal integrity to shrug off abuse of power because of their rules and norms.