I would guess the liberal governors will argue that Mr. Greenfield’s conclusion that Brown et. al. are in violation of the Constitution is incorrect on the basis that the Paris Climate Accord is not a “treaty” in the understood meaning of this word.
http://www.heritage.org/constitution/#!/articles/1/essays/69/state-treaties
Based on this commentary, I think it would come down to exactly how Brown et. al. enjoin with the foreign nations in this accord. If he attempts to pledge California’s involvement in such an accord, I think he is violating the US Constitution. Conversely, if he merely agrees to actions in kind with such an accord, but doesn’t explicitly join it, I think he will skirt the Constitutional question.
Obama decided to lie and call it an agreement, but it is a governmental commitment to provide material support to outside entities - thereby intended to obligate the congress to appropriate those funds. Underlying all of this is Obama's deception on this not being a treaty.
The material you posted does not appear to me to diminish that the Paris accord was actually a treaty, although Obama desperately wanted people to not see it that way.