The nonproliferation "regime" may now be collapsing. That doesn't mean we should precipitously abandon it. We have an interest in slowing the proliferation of nuclear weapons, and the nonproliferation regime remains one tool of persuasion. But as in the past, and as always in international affairs, there must be some adjustment to reality. One aspect of the present reality is that India has long been a nuclear power, and this deal doesn't make it more of one. Another part of the present reality is that North Korea and Iran are probably going to be nuclear powers, too, and in any case the nonproliferation "regime" is not going to stop them.

Were Congress somehow to reject the administration's deal in some effort to maintain a consistent principle on nonproliferation, it would have no effect on Iran's decisions. But that futile gesture would have a devastating effect on U.S. relations with India. In our less-than-ideal world, where, we are often told, America needs good friends and allies, that would be a terrible bargain.