There should be no justification of going to war unless the opposing side is harming your country and countrymen, economically, physically, or by isolating you. But as a politician anything that economically benefits my country would be justified if me going to a war. Taylor, had done the same during the Spanish American war by blaming Mexico of stealing Texas back, even though the land was Mexico's back then. He'd done it to enlarge America's land, Manifest Destiny. He spread the propaganda that Mexican troops attacked American, which emotionalism do Americans and they ended up backing up Taylor's decision of going on a war.
The Kyoto Treaty does not undermine the United States sovereignty because it does not have anything to do with such. It was a treaty that asks committing State parties to reduce greenhouse gas emissions because global warming does exist and it is caused by CO2 productions done by human activities.
The answer to you question would be secretary of war.