First off, Carter probably didn't trust Kim any further than he could throw him. But Carter understands the art of the deal. You give someone something valuable, you get something valuable in return. At some point "Trust but Verify" breaks down and you just have to hope that the other guy understands his best interest.
"Hey guys, they want to build nuclear reactors for us if we promise not to develop nuclear weapons...I know, let's do it behind their backs and save some money!"
Have you read the treaty? Or are you just going on what you've heard?