Story here.
Thing is, this “status of forces” agreement is not a treaty, therefore does not require Senate approval.
But, in that case, is it legally binding on the U.S. government, and especially on the next administration, or is it not?
(This might be moot – the story says the Iraqi Parliament almost certainly will reject the agreement in its present form.)
This is what is called an “executive agreement.” The law on executive agreements is pretty thin. This answers.com page offers a surprisingly good summary.
There are two big hurdles to overcome for such an agreement to be binding on the next President.
First, the content of the agreement would have to be considered part of the President’s inherent foreign affairs power. This is probably doable, but as you know there is some debate about whether the Congress has some power to withdraw troops other than by cutting off all funds.
The bigger obstacle is the binding aspect. The case law is all about who the President can trump because of his inherent power (Congress, states, the judiciary). But trumping a latter holder of the same office is an entirely different matter. I suppose the best argument that it would be binding is that the armistices negotiated by executive agreement should also be binding–what’s the point of an armistice if, after an election, your country can renege? But, of course, this argument would be diametrically opposed to everything the Bush administration has ever said about the binding nature of international agreements of any kind.