David Sanger's article in the New York Times about how the Obama administration is seeking a nuclear accord with Iran that would not require any early votes in Congress has garnered a lot of attention. Naturally, the administration in response has offered assurances that Congress has a role to play and no one is trying to shove it out of the picture. Just as naturally, opponents of the administration accuse it of such shoving.

We all know what's going on and what's at stake here. The more of a role Congress does play in the immediate aftermath of signing a deal, the greater the chance that elements opposed to anyone reaching any agreement with Iran on anything will be able to torpedo the deal. This is reflected in the substantial record Congress has already compiled, as cataloged by Navid Hassibi's review of that record, of past attempts that would impede the negotiations. It also is reflected in the fact that some of those quickest to complain about a supposed offense to Congressional prerogatives on this matter are those who have been most determined all along to sabotage any agreement with Iran. So for anyone who realizes the advantages of having a deal to restrict Iran's nuclear program versus not having a deal, the less Congressional involvement right now the better.

A major caveat to this conclusion is that any lack of confidence on the part of the Iranians in the staying power of a deal in which the the United States fulfills its part of the bargain only through executive action may also make it harder to complete the negotiations. If the Iranians believe all they are getting in the way of sanctions relief is tentative and reversible, in an accord that can be undone by Congress or a later president, they understandably will be reluctant to offer anything other than tentative and reversible things in return. This is why the assertion that has routinely accompanied past efforts to slap more sanctions on Iran during negotiations—that this supposedly would increase U.S. bargaining power—is fallacious (and if it really did increase, why wouldn't any president want to have the added power?) Instead, the effect would be to make negotiations more difficult by increasing Iranian doubts about the administration's ability to fulfill U.S. commitments. Probably the best way to deal with all this is to rely, as Hassibi suggests, on the combination of a couple of years of compliance with an agreement and confirmation of its terms in a United Nations Security Council resolution to make the saboteurs' task harder.

None of this appears to be really about high constitutional principles concerning the relative powers of branches of the U.S. government. It is about whether the United States is going to seize or to blow the best opportunity to preclude an Iranian nuclear weapon and to do it in a way that will have other benefits for U.S. interests in the Middle East. There are, nonetheless, some more principled things to say about the role of Congress on different types of national security matters.

Consider the issue of the Iranian negotiations alongside another subject on which relative powers of the legislative and executive branches have received considerable attention: the use of military force. One legislator whose stance is worth looking at is Senator Tim Kaine of Virginia. Kaine has taken a responsible position regarding the Iran negotiations, opposing any Congressional interference with them in the form of new sanctions. He also has become quite an activist in asserting a Congressional prerogative to approve or disapprove the use of military force. In fact, he has broken openly with the president of his own party by arguing that the current use of force in Syria and Iraq should have first obtained Congressional authorization. Kaine's positions should be emulated, and here's why.

There is good reason that the Constitution placed the power to declare war with the people's representatives in Congress. It is a major and potentially highly costly departure. Expending blood and treasure in warfare is one of the riskiest and most consequential things the nation can do. As has been demonstrated painfully and recently, going to war has a way of dragging the nation into even costlier and longer-lasting commitments.

An agreement of the sort being negotiated with Iran is none of those things. The agreement would impose no new costs on the nation; in fact, it would involve reducing the cost that sanctions inflict on the United States. It does not create, as warfare does, any new exceptions to normal peacetime relations with other states; instead, it would be a move toward restoring normality. It does not, as do some other matters that are appropriately codified in treaties subject to Senate confirmation, impose any new legal obligations on U.S. persons; instead it is a step toward reducing the costly and cumbersome restrictions on U.S. business that the sanctions involve. It does not mark a departure in national goals and objectives, because it is an almost unanimously shared objective that Iran not acquire a nuclear weapon. The issue instead is what is the best way of executing policy to achieve that objective; that is part of what the executive branch is supposed to do.

Recognition of that last point is reflected in the laws about sanctions that give the president waiver authority and thus the flexibility needed to achieve the objectives that the sanctions were supposed to be all about. Those were laws that the U.S. Congress enacted. That is why it is ridiculous for Representative Ileana Ros-Lehtinen—one of the most consistently Iranophobic hardliners in Congress—to say, as she does in a “dear colleague” letter she is circulating, that the president is “circumventing” Congress by making use of waiver authority that is written into sanctions legislation that she sponsored.

There is a time and place for Congress to assert itself, and different times and places for it to defer to the executive branch in execution of its proper functions.