Iran continues to engage in a range of missile activities that directly threaten U.S. forces and allies in the region. The ballistic missile fired at the Saudi capital of Riyadh on November 4, assessed by the United States as an Iranian missile provided to the Houthi government in Yemen, serves as a stark reminder of how Iran’s missile efforts contribute to regional instability. Critics of the Joint Comprehensive Plan of Action (JCPOA), including the Trump administration, contend that Iran’s missile activities are evidence of the JCPOA’s failings. This perceived deficiency served as part of the basis for President Trump’s October 13 announcement that he would no longer certify that the JCPOA serves the vital interest of U.S. national security, in spite of the public statements of cabinet officials to the contrary. The Trump administration’s Iran strategy commits to countering Iran’s ballistic missile threats, but doesn’t say how it would do so. Continuing to enhance regional missile defense appears to be a component of the strategy, and is certainly necessary in reducing the damage Iran’s missiles could pose. But part of the challenge from Iran’s missiles is a growing inventory that could saturate defenses to hit their targets. There are a number of tools the United States can employ to limit the dangers from Iran’s missile program. Use the JCPOA to Addresses the Priority Missile Threat The most dangerous threat a ballistic missile could pose is that it is armed with a nuclear weapon. For that reason, U.S. and international ballistic missile nonproliferation policy is focused on stopping the spread of missiles “inherently capable” of delivering nuclear weapons—defined as missiles capable of delivering a 500-kilogram payload at least 300 kilometers. By effectively cutting off Iran’s pathways to a nuclear weapon through limits on Iran’s nuclear activities and extensive verification, the JCPOA is one of the most important tools the United States has to reduce the threat of Iran’s missiles. Rather than risk upending the agreement by imposing sanctions lifted for Iran’s continued compliance, the Trump administration and Congress should faithfully enforce it. The United States should also begin thinking of ways to continue to constrain Iran’s nuclear program once the JCPOA provisions begin to expire, to ensure that the payloads Iran can put on its ballistic missiles remain conventional. Win Support for Shutting Down Missile Middlemen Iran maintains a sophisticated proliferation network to acquire sensitive technology. Such networks often have key middlemen linking procurement agents to suppliers. Perhaps the most significant of these individuals is Chinese national Li Fangwei, better known as Karl Lee. The United States has called Lee a “principal contributor” to Iran’s missile program and has long sought to convince Beijing to shut down his activities. After direct engagement with China failed to garner action by Beijing, the Obama administration began a public campaign against Lee in April 2014. This campaign included a $5 million reward for information leading to Lee’s arrest or conviction, and was coordinated with Lee’s indictment by a New York federal court for violating U.S. export controls and laundering funds. Beijing subsequently agreed to more discussions on Lee’s activities, but these do not appear to have borne fruit. While Lee is hardly the only middleman aiding Iran, ending his proliferation activities would cause a blow to Iran’s procurement efforts, and would be an effective use of President Trump’s relationship with President Xi. UN Missile Controls Expire, U.S. and Multilateral Controls Do Not Because UN Security Council (UNSC) missile restrictions were tied to Iran’s nuclear program, reaching agreement on the latter meant that those sanctions would be unwound, especially with no appetite from Russia and China to maintain them. As a result, prohibitions on transferring missile-related goods to Iran sunset after eight years, or when the IAEA certifies that there are no undeclared nuclear activities in Iran—the so-called “broader conclusion.” The UN missile restrictions on Iran codified previously ongoing efforts to stop Iran’s missile procurement. Their benefit was providing the legal basis some countries claimed they needed to take action against suspicious Iranian shipments. Since so much of Iran’s procurement activities involve the transfer of dual-use goods that many states have difficulty controlling, countries were far more comfortable stopping suspect transfers when they could point to specific UNSC provisions, or even better, items on the UNSC Iran blacklist. The practical impact is that when the United States and others share information with another state about a suspect Iranian shipment, that state may be more hesitant to inspect it because it is no longer an explicit legal obligation. Instead, those states will need to be convinced that inspecting and seizing smuggled missile parts is what responsible states do. Encouraging such action against proliferation is why the United States has worked to build coalitions of responsible states in bodies like the Missile Technology Control Regime (MTCR) and Proliferation Security Initiative (PSI), which are poised to continue halting Iranian missile trafficking irrespective of the sunsetting UN restrictions. In fact, U.S. officials declared after the JCPOA was concluded that such tools would by the JCPOA. These tools include the sanctions the United States has continued to levy on those supporting Iran’s missile program. Moreover, while UN restrictions on Iran’s missile activities expire, UNSC sanctions still prohibit Iran’s missile cooperation with North Korea. Countries seeking to do business in Iran should tell Tehran that its continued missile cooperation with North Korea will put any potential economic ties at risk. This is an especially important message coming from South Korea and Japan, which have had considerable economic ties with Iran and face direct threats from North Korea. Open the Door to Building on the JCPOA with Missile Negotiations Iran’s missiles were not expressly addressed in the JCPOA for several valid reasons. U.S. negotiators have indicated that the matter was rejected early on by Iran as a deal-breaker. Moreover, there was little support by U.S. negotiating partners, particularly Russia and China, meaning there was little pressure on Iran to change its stance. So long as the agreement is upheld, it can be used as a foundation for discussions on missiles. Iran’s declaration in October that it did not see a need to field missiles ranging beyond 2,000 kilometers can serve as a potential opening. At the very least, it indicates Iran’s recognition that other countries are concerned about missiles capable of hitting targets outside the region, as these longer-range missiles have historically indicated a desire to deliver nuclear weapons. Chances are slim, however, that Iran would limit its missiles’ ranges without a broader regional arms control mechanism given the military, missile, and nuclear capabilities of countries nearby. It may be better to focus such negotiations on destabilizing missile activities that remain prohibited under international law, and are less central to Iran’s direct self defense. Beyond the UN’s North Korea sanctions, the UNSC has also adopted arms embargoes on the Houthis and Lebanese Hezbollah. Negotiations based on the principle of enforcing UN arms embargoes should be something to which all UNSC members can agree. Conclusion Short of a military occupation, the United States is not going to rid Iran of ballistic missiles. It can slow the progress of that program, and seek to negotiate restraints on the missiles Iran fields and how it acquires them. Most importantly, a serious Iran strategy must identify the priority threats that must be stopped, even as other threats are addressed. That priority threat is an Iran that can place nuclear warheads on its missiles. The United States should keep the international community united around that goal by enforcing the JCPOA, increasing the chances that other countries join in countering other dangers from Iran’s missiles.