"The multilateral nuclear accord (Joint Comprehensive Plan of Action, or JCPOA) provides Iran broad relief from U.S., U.N., and multilateral sanctions on Iran's civilian economic sectors. On January 16, 2016, upon the International Atomic Energy Agency (IAEA) certification that Iran had complied with the stipulated nuclear dismantlement commitments, U.S. Administration waivers of relevant sanctions laws took effect, relevant executive orders (E.O.s) were revoked, and corresponding U.N. and EU sanctions were lifted ('Implementation Day'). Remaining in place have been those secondary sanctions (sanctions on foreign firms) that have been imposed because of Iran's support for terrorism, its human rights abuses, its interference in specified countries in the region, and its missile and advanced conventional weapons programs, as well as sanctions on the Islamic Revolutionary Guard Corps (IRGC) and designated commanders, subunits, and affiliates. [...] As part of a shift to assertively counter Iran's regional activities and strategic weapons programs, the Trump Administration has designated for sanctions additional missile and IRGC-related entities. The Administration asserts its steps do not conflict with U.S. commitments under the JCPOA and the Administration has continued to implement the agreement, including renewing waivers of sanctions laws suspended in accordance with the JCPOA. Were the Administration to decide to end U.S. participation in the JCPOA, it could revoke waivers, decline to renew waivers, or trigger a provision of the Iran Nuclear Agreement Review Act (P.L. 114-17) under which Congress might act on legislation to reimpose sanctions."
CRS Report for Congress, RS20871
Federation of American Scientists: http://www.fas.org/sgp/crs/index.html