This bill would prohibit any sanctions on Iran from being lifted unless the Senate approves the Iran nuclear deal (AKA the Joint Comprehensive Plan of Action (JCPA)). The approval would have to come through a two-thirds vote as if the JCPA were a treaty.
Under current law, the JCPA is being treated as an executive agreement rather than a treaty. This means that instead of having to get a two-thirds approval from the Senate, the President can unilaterally enter into the agreement. So, this bill essentially applies the Treaty Clause of the Constitution to the JCPA.
This bill would only apply to sanctions imposed by the U.S. — so foreign governments could still relieve sanctions on Iran.
As soon as this bill is enacted it would take effect, and would apply to sanctions relief provided by the U.S. before, on, or after that date. In practice, this could require the U.S. to re-impose sanctions that had been lifted by the JCPA without the Senate’s approval.