Sanctions could be reinstated in several ways. Congress could introduce legislation to reimpose sanctions within 60 days of the deadline for certification. Such legislation would be entitled to INARA’s expedited consideration procedures. Alternatively, the president could decline to exercise the waivers that have suspended the implementation of sanctions legislation thus far. The president could also reinstate designations of Iranian persons and entities as Specially Designated Nationals (SDNs) pursuant to executive order. Such designations would also trigger secondary sanctions like those provided for in the Comprehensive Iran Sanctions, Accountability, and Divestment Act of 2010, a law that restricts the access of third-country financial institutions with ties to Iran-related SDNs to the U.S. market. Finally, the United States could move to reimpose U.N. sanctions by triggering the “snapback” mechanism agreed upon in the JCPOA (more on that here). So far, the administration has not indicated that it intends to take any of those steps to unilaterally reimpose sanctions. …

The president does not really need Congress in order to reinstate sanctions that were lifted in the framework of the nuclear deal. He can do so by exercising authorities that he already has through waivers or executive orders.