I'd sure like to know where these people think they have the Constitutional authority to make deals like this."
Here's your answer:
"He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur" - Article 2, Section 2
But, the "two thirds of the senators present" are supposed to have the support of the people they represent, which I don't believe they have.
This is government without the consent of the governed and when the time comes, the government will be ready to use force to enforce it.
After all, anyone who doesn't like it will be labeled a right wing militant.