Tyler Cullis is a Policy Associate at National Iranian American Council.] Introduction We’ll soon find out whether the decade-old nuclear dispute with Iran can be resolved diplomatically, as the parties return to Vienna next month to hammer out a comprehensive agreement. So far, negotiations have been deftly handled by both US and Iranian negotiators – the positive atmosphere, so critical to staving off domestic opposition, having been maintained over several months. But still, the most difficult issues remain on the table, including the number (and type) of centrifuges Iran will be permitted, the duration of a final agreement, and the timing of sanctions relief. Successfully concluding a nuclear deal will require compromise from both parties on each of these issues. While much attention has zeroed in on Iran’s obligations under a final deal, few have discussed the specific modes by which the US will comply with its own commitments. This is troubling, especially insofar as the White House’s ability to provide Iran measurable sanctions relief, absent an affirmative act of Congress, is not assured. In fact, relieving the sanctions will involve difficult questions of law and policy that deserve far more extensive discussion than received at present. Below, I discuss a few of these issues, posing as they do hurdles perhaps as sizeable as Iran’s own centrifuges. Treaty or Not to Treaty? Soon after the Joint Plan of Action was inked in Geneva last November, questions arose as to the legal nature of the preliminary agreement: Was it binding as a matter of international law? If so, would it need to be submitted to the Senate (or, in Iran’s case, to the Majles) for approval? Consensus, here and elsewhere, said no: the interim deal was left unsigned by the parties and had couched its commitments as “voluntary measures,” not mandatory ones. This, it was argued, signified that the P5+1 and Iran did not intend for the document to be either binding on the parties nor governed by international law. Drawbacks to this approach were obvious, but the upside was that each of the parties avoided the need for legislative approval at home (Iran, too, has constitutionally-mandated procedures to follow before an international agreement can be entered into and take domestic effect). Now that we are more than halfway through the interim period and both parties remain in full compliance with their “voluntary” obligations, the choice of informal agreement looks to have been the correct one. Going forward, however, the central question will be whether the parties replicate this model in a final deal or instead cement a binding international agreement (i.e., a treaty). While the White House remains keen on insulating Congress as much as possible from playing spoiler and is thus unlikely to submit a final deal to the Senate for approval, there are several factors that ward against replicating the “soft law” nature of the Joint Plan of Action. First, because the US will be required to offer more lasting sanctions relief than that provided under the Joint Plan of Action and, as of now, the President is limited in the kind of sanctions relief he can provide, Congress will be called upon to lift the sanctions at some point in this process. Whether to include Congress at the front- or back-end of a final deal remains a strategic question for the White House, but avoiding Congress altogether is no longer a plausible scenario. (Nor is more aggressive action from the White House likely. It is improbable that the White House will attempt to conclude a sole executive agreement with Iran that overrides contrary federal law and gives the President the authorities he needs to provide Iran the requisite sanctions relief. Such a step would prove a legal leap beyond that of Dames & Moore -- the President not acting pursuant to Congressional authorization or acquiescence but rather in ways contrary to Congress’s clear direction.) Second, unlike the interim deal, which was intended as both a confidence-building measure and a place-holder to allow the parties time to negotiate a final deal, the final agreement will be one where the obligations actually matter.