Day by day the debate on the Iran nuclear deal drifts further into the deep weeds. Iranian Foreign Minister Javad Zarif last week announced his expectation that the agreement will “be endorsed by a Security Council resolution,” leading to speculation that the Council could transform a non-binding agreement into a binding one and handcuff future US presidents. The agreement also slights the legislative branch, it’s contended; Senate or congressional approval, it’s said, is constitutionally required.

Three matters warrant clarification: the role of the Security Council, the effect of its resolutions under US law, and the status of non-binding agreements under US law.

The role of the Security Council. First, “endorsement” by the Council could mean virtually anything. The mere fact that the Council adopts a resolution, even one that constitutes a “decision” taken under Article 25 (and thus obliges member states to comply), does not mean that any member state automatically assumes a legally binding obligation. Whether a given resolution imposes an obligation depends entirely upon its wording. No draft Iran resolution has yet been publicly disclosed, and the administration has disclaimed any intent to convert the agreement into a binding obligation through a Security Council resolution. Many of the Council’s resolutions have in fact been merely hortatory or commendatory, or merely take favorable note of specified events or occurrences. On April 11, 1995, for example, the Council adopted Resolution 984, indicating that the Council “[t]akes note with appreciation of the declarations made by each of the nuclear-weapon States” concerning their (qualified) intent not to use nuclear weapons against non-nuclear-weapons states. However, the United States has considered its declaration on the use of nuclear weapons (like an earlier one on the subject made in 1978 and a later one made in 2002) not to be legally binding. None of those declarations was transmitted to Congress under the Case Act, which requires the transmittal of all international agreements. None was registered with the United Nations under Article 102 of the Charter, which requires that every international agreement be registered with the Secretariat. The “endorsement” of the 1995 US declaration by the Security Council thus had no effect in making the declaration legally obligatory under international law. The declaration was and is a political undertaking, not a legal commitment.

Second, involvement by the Council — which is unavoidable if UN-imposed sanctions are to be suspended — could in fact tighten the screws on Iran. Secretary of State Kerry, in his testimony before the Senate Foreign Relations Committee March 11, referred to the agreement’s “capacity for enforcement.” He might have had in mind the argument made by the United States for resurrecting authority to use force against Iraq prior to the Second Gulf War. The United States argued that Iraq’s alleged material breach of the Council’s cease-fire resolution, Resolution 687, resulted in the extinction of that cease-fire and caused the earlier measure that authorized use of force during the First Gulf War, Resolution 678, to spring back into effect. Kerry might believe that a parallel process can be made explicit in a new Security Council resolution that lifts UN-imposed sanctions on Iran — which could provide that those sanctions will automatically be reinstated if Iran breaches the new nuclear deal. Whether other members of the P5+1 would agree to a “snapback” provision remains to be seen, but given the criticism directed at the United States for its “unilateral” interpretation of the resolutions applicable to Iraq, it would clearly redound to the United States’ diplomatic advantage to avoid getting painted into a similar corner with Iran. Deft footwork in the Security Council can prevent that.

The effect of a Security Council resolution under US law. Suppose, however, that the Council were to adopt a new resolution mandating compliance with the agreement in a decision taken under Article 25 of the Charter. Could that not bind a future president under US law to, say, waive the application of US statutorily-imposed sanctions even though Iran, in his or her view, has failed to comply with the agreement? The answer is no. Under domestic law a Security Council resolution does not require presidential compliance. Recall the Supreme Court’s observation in Medellin v. Texas, 552 U.S. 491 (2008), that the UN Charter does not create binding federal law in the absence of implementing legislation, and that no such legislation has been enacted. Medellin also announced a corollary rule that exempts non-self-executing treaties from the operation of the Faithful Execution Clause because such treaties are not domestic law. Making the agreement binding through a Security Council resolution could therefore not accomplish the putative objective of requiring a future President to take care that the agreement be faithfully executed. A subsequent executive order would control.

Even if a Security Council resolution were binding under domestic law, its obligations could always be overridden in domestic law by a later-in-time enactment of the Congress. This was made clear in 1972 when Congress enacted a statute that required the President to resume trade with Southern Rhodesia in violation of an earlier Security Council resolution that imposed an international embargo. The D.C. Circuit in Diggs v. Shultz, 470 F.2d 461 (1972), upheld the statute — even though it had been “presented to the Congress” as “a measure which would make — and was intended to make — the United States a certain treaty violator.” The court continued:

It is settled constitutional doctrine that Congress may nullify, in whole or in part, a treaty commitment. Congress [in this statute] acted to abrogate one aspect of our treaty obligations under the U.N. Charter, that is to say, our continued participation in the economic sanctions taken against Southern Rhodesia … .Thus, appellants’ quarrel is with Congress … .

Within the domestic legal system, in other words, Congress can shape how — or whether — an international obligation is implemented. The only exception is an obligation that flows from the exercise of plenary presidential power, such as the power to recognize or de-recognize another nation. Accordingly, if he was referring to US domestic law, Kerry was in error in testifying that the Cotton letter was

incorrect when it says that Congress could actually modify the terms of an agreement at any time. That’s flat wrong. They don’t have the right to modify an agreement reached, executive to executive, between countries — between leaders of a country.

Congress clearly does have the authority under the Constitution to change statutory law — even if the change would cause federal law to conflict with a binding treaty obligation, let alone a mere political undertaking that rests upon statutorily-delegated waiver authority. It is an instrument’s status in international law that would not be affected.

The status of a non-binding agreement under US law. Does the nuclear deal require Senate or congressional approval? Much the same question arose in 1977 upon expiration of the SALT I Interim Agreement of 1972. Parallel statements were made by US and Soviet officials indicating that each nation would take no action inconsistent with the provisions of the expired Agreement (which had been approved by Congress). Critics claimed that the Executive was making a new, binding international commitment that required renewed Senate or congressional approval. But none was either sought or given. The matter was resolved when the administration made clear, in communications to the Senate Foreign Relations Committee, that the US statement was non-binding and non-obligatory, that each nation had stated only a “present intention to refrain from certain action provided the other refrains from similar action,” that each was “free to reverse its intention at will,” and that “there would be no legal consequences if either changed its stated policy.”

That will be the posture of the United States with respect to the Iran nuclear deal. The administration has made clear that the agreement with Iran, like the 1977 US SALT I declaration, will be non-binding. In his testimony before the Senate Foreign Relations Committee last Wednesday, Kerry said flatly that it is not binding:

Now, with respect to the talks, we’ve been clear from the beginning. We’re not negotiating a, quote, “legally binding plan.” We’re negotiating a plan that will have in it a capacity for enforcement. We don’t even have diplomatic relations with Iran right now. And the senators’ letter erroneously asserts that this is a legally binding plan. It’s not.

That commitment, taken in combination with last week’s commitment not to make the agreement binding by means of a Security Council resolution, should end the constitutional debate about a supposed need for approval. There is none.

Among the tasks that remain, however, is to get the Iranians onto the same page. Zarif, this past week, seemed not to have gotten the memo on the agreement’s non-binding status. States, Zarif said, are required to “fulfill the obligations they undertake with other states,” and he worried about Congress committing a “material breach of US obligations.” He warned that “if the next administration revokes any agreement with the stroke of a pen, as they boast, it will have simply committed a blatant violation of international law.” Zarif needs to understand that that’s not the way the United States sees it, and that under international law the United States will not incur a legal obligation to which it does not consent. But in principle that should not matter to Iran. Iran can get the continuous sanctions relief it wants in a non-binding deal. The P5+1 can get the restraints on Iran’s nuclear program that they want in a non-binding deal. The reason, as Secretary Kerry pointed out, is simply that — as a purely political matter — the parties to the agreement will have every incentive to honor an agreement that is giving them what they want. This — in principle — is a fully adequate, reciprocal “capacity for enforcement.”

In the meantime, members of Congress would do well to familiarize themselves with long-standing US practice concerning the use of non-binding international agreements. That practice does not lend support to the redundant Senate or congressional role for which some argue. Congress has, after all, already approved presidential waivers, without which no deal with Iran would be feasible. Had Congress wanted a second bite at the apple, the sanctions statutes could have required the President to come back to Congress for waiver authorization. But their waiver provisions contain no such requirement. It’s a bit late in the game for members of Congress to complain that the President is exercising the very power that they explicitly gave him. But it’s not too late for Congress to stop acting generally as an adjunct of the Executive in national security matters and to begin exercising a responsible “will of its own” — as the Constitution’s Framers contemplated.