Earlier this month, Rafael Grossi, the director-general of the International Atomic Energy Agency, or IAEA, traveled to Tehran amid growing concern over the proliferation risk posed by Iran’s expanding nuclear activities. In particular, the IAEA had recently detected uranium enriched to 84 percent in an Iranian nuclear site, at a time of heightened tensions due to the breakdown in multilateral talks on reviving the Iran nuclear deal. During Grossi’s trip, Iran agreed to allow the IAEA to reestablish certain transparency measures at select nuclear sites. Iran had suspended IAEA access and...