How about a Declaration of War instead, or would that require there to be some threat to the US?
Declaration of War? That’s a quaint idea. When is the last time the US, or any nation for that matter, formally declared war? The president has constitutional authority over our forces, Congress controls the purse strings, and we, the public, can vote him out of office if we don’t like his actions. Trump does not need Congressional permission, nor the UN, or anyone else’s to launch an attack anywhere, anytime.
Using chemical weapons is a threat to everyone. But do you declare war on your kids for sword fighting each other with butcher knives, or just spank them and send them to their rooms.