[tsimionescu]

Of course you can. If a country commits to signing an international treaty, the normal expectation should be that it considers itself bound by that treaty, for some time at least. A normal president can't just go and overrule the previous president's words unilaterally, for the very simple reason that I illustrated: it makes it impossible to take anything the country signs seriously. Why would anyone accept a compromise deal with Trump on anything that has repercussions beyond 2028 knowing that the next president will just ignore it?

I should note that, on this particular ground, I don't necessarily blame Trump as the one who backed out of the deals. It's very much possible that the blame should rest on Obama for signing a deal he knew had insufficient support in his country and wouldn't be followed through by his successors. If he were an honest man, he wouldn't have signed the deal in this case, even if he believed (as I do) that the deal is critically important for the future of the world. Falsely committing to do the right thing is no less dishonest than going back on a word you gave.

[renata]

Treaties specifically have to be approved by Congress and have approximately the same force of law and durability as the Constitution. Lately we mostly do "executive agreements" instead, which do not require Congressional approval and can pretty much be ignored on a whim by the next president. We could go back to treaties but considering Congress has given up so much of their responsibility to executive agencies because they can't even pass laws, it seems unlikely.