The Trump tariffs failed because of his failure to gain approval from Congress, but he might as well have lost the case on failure to establish an emergency. The real emergency that US citizens face right now, like the rest of the world, is the state the global environment, and for that the United Nations needs to act. The UN needs to act on its own emergency powers to make rules around the control of human caused pollution. While there are no emergency powers, as such, in the UN Charter, there are powers in it for the UN to do anything it takes for the UN to protect the security of mankind. Right now, that means to make rules to protect the environment, and to enforce them. Now that would be lawful.