There are many reasons why President Trump must pull the United States from the Paris Climate Accord some of which include the facts that 1) Man Made Climate Change is a hoax - weather patterns are controlled by sun patterns, 2) It is a job killer that will weaken the U.S. Economy bankrupting us and 3) it is a back door TREATY that by-passes the required 2/3rd vote to be ratified by the U.S. Senate. Obama knew this which is why he hurried to get us into the accord.
Here is a dirty secret in 1969 There was a United Nations gathering in Vienna to sign the Treaty on Treaties. The Treaty on Treaties was the frame work of how Treaties should be handled even if not fully signed by all willing or considered willing participating coutries.
Yes considered willing countries, if a country is considering some or all of a Treaty according to the Treaty of Treaties section 18 you are basically ratifying the Treaty when you agree to all or party the treaty even if you haven't signed the treaty .
This is why Trump must pull us out of the Paris Climate Accord as it is a treaty in its own right and under the Treaty of Treaties section 18, if we agree with any part of it verbally we are considered bound, Now since the accord was agreed to by Obama but not passed by 2/3rds of the U.S., Trump has the ability to undo Obama's agreement. However if he does not pull out, we could be stuck with being in the Paris Climate Accord unless we get 2/3rds of the Senate to pull us out.
Trump can save face by saying that we are pulling out of the Accord, as it is considered a Treaty, and it must be passed by 2/3rds of our Senate. There it will likely die and President Trump won't have to take the blame as he alone didn't make the decision to get out of the Paris Climate Accord alone but wanted the U.S. to accept the accord/treaty under the laws of our Constitution.
Here is the clause of the 1969 Vienna Convention Treaty on Treaties, which by the way never was ratified either by 2/3rds of the U.S, Senate.
Article 18. OBLIGATION NOT TO DEFEAT THE OBJECT AND PURPOSE
OF A TREATY PRIOR TO ITS ENTRY INTO FORCE
A State is obliged to refrain from acts which would defeat the object and pur
pose of a treaty when:
(a) It has signed the treaty or has exchanged instruments constituting the treaty
subject to ratification, acceptance or approval, until it shall have made its in
tention clear not to become a party to the treaty; or
(b) It has expressed its consent to be bound by the treaty, pending the entry into
force of the treaty and provided that such entry into force is not unduly