We should all recognize that there is a difference between the policy of any agreement with Iran and the constitutional law that governs the agreement. We can have different views about the best way to contain Iran’s nuclear ambitions without having to disagree on the constitutional foundations of sole executive agreements or a senator’s right to voice his or her personal views about the Constitution. For what it’s worth, one fix for the controversy would be for Senator Cotton to offer a resolution on the floor of the Senate opposing any nuclear deal with Iran that does not undergo advice and consent — that would clearly fall within his and the Senate’s constitutional authorities and would settle the matter.

Some are criticizing the Cotton letter for attempting to interfere with the president’s “sole organ” authority to conduct the diplomacy of the nation. But I don’t think the president’s sole organ authority, first articulated by John Marshall (as a congressman) and approved by the Supreme Court (in U.S. v. Curtiss-Wright Export Corp in 1936), prohibits senators from making clear their positions on foreign-policy matters. Senators can take votes that might oppose an executive-branch policy. For example, the Senate passed a resolution opposing the Kyoto Accords, which effectively killed any chances of that treaty, and the American Servicemen’s Protection Act, which essentially defeated any hope for the International Criminal Court’s ratification by the U.S.

I of course have defended the sole-organ authority of the president, probably more vigorously than any other law professor and few other government officials. But here the senators are not trying to negotiate with Iran or even trying to set out any terms for a deal. I thought the letter tried to avoid any substantive terms of the deal, but only went as far as stating clearly U.S. constitutional law (which I expect the Iranians would know or would have paid advisers who would know). As a description of our constitutional law of international agreements, the letter was correct. What is the effective difference of sending the Constitution to the mullahs in an envelope, giving a speech reminded President Obama of the law of treaties, or, publishing an op-ed criticizing the sole executive agreement? What would be best, now, would be for Senator Cotton to offer a Senate resolution opposing any sole executive agreement to limit Iran’s nuclear capability.

Some have also argued that this is partisan, and would not happen if the shoe were on the other foot. I can say, from personal experience, that this is not true. When President Bush was negotiating the Treaty of Moscow with Russia, which resulted in deep cuts in nuclear arsenals, some in the State Department floated the idea that the White House should execute it as an executive agreement. Senators Biden and Helms issued a statement that the agreements should undergo the treaty process, as all significant arms-control agreements have in the past. John Bolton (at State) and I (at Justice) agreed, and the deal was executed as a treaty with the advice and consent of two-thirds of the Senate.

A different point may be that one can object to senators issuing communications to foreign leaders at all or hold that they shouldn’t undermine executive-branch policy in foreign affairs. I don’t see that as as much of a problem as others might, because Senators have the right under the speech-and-debate clause to say whatever they like. So I thought it a serious policy problem for Senators Clinton and Obama to attack General Petraeus in hearings during the surge and to predict defeat for our troops, but I don’t doubt that they had the constitutional right to voice those opinions in Senate hearings, on the floor of the Senate, in speeches outside the Senate, or in writings in the national newspapers. If those senators have that power, I don’t see why Senator Cotton cannot take the position that an international agreement without the Congress’s approval is short-term only.