International law is based on the principal that sovereign nations should be permitted to unilaterally govern their societies unless their activity impermissibly infringes the sovereignty of another nation. With climate change debt those nations emitting the most carbon into the atmosphere and causing the most global warning are doing so at the expense of other nations' sovereignty, which did not have a say in global warming.
Climate change is a huge issue to some. To others, it's a non issue. And that is where the problem lies. Even in America, the most powerful nation on earth, much of the population believes climate change isn't a big deal. So we expect to put an international climate change law, while one of the world leaders can't even come to a consensus? Not likely.