With ISIS vanquished and Iraq’s security forces reconstituted and reorganized (thanks to U.S. training and support), some expected that Sistani would revoke his fatwa and dismantle the PMF last December. But Sistani cannot simply dissolve the PMF, a state institution that provides livelihoods and prestige to its fighters. Doing so would spark a public backlash and undermine Iraq’s Shiite clerical establishment. Neither can he confront Iran’s proxies alone as they, and Shiite militias more generally, have proved themselves formidable actors. (The United States tried with more than 100,000 troops during the occupation and failed.)

But left untouched, Iran’s proxies will continue exacerbating sectarian tensions that could very well enable the resurgence of ISIS. Sistani will have to confront them eventually—but not by himself, and not in the way some may expect.

Essential to the Shiite militias’ survival over the years has been their capacity to adapt to the political and legal constraints imposed on them. They either attach themselves to longstanding parties or rebrand themselves as socio-cultural movements that provide social services to local, often destitute communities. Groups like Asaib ahl al-Haq, which has been complicit in attacks on U.S. and Iraqi personnel and civilians, were established by Iran after 2003 and have since transitioned into powerful armed groups that enjoy access to state institutions and resources, yet continue to function autonomously. Iran-aligned Shiite militias have, in essence, established themselves as Iraq’s version of Lebanon’s Hezbollah: socio-cultural movements with a military and social-welfare wing that operates independently of the state.

Asaib al-Haq is not the only Shiite militia in Iraq that has benefitted from Baghdad’s resources without ever submitting to its control or to civilian oversight. Another prominent example is the Badr Brigade, an organization established by Iran during the 1980s Iran-Iraq war. While it began as a militia, since 2003 it has controlled Iraq’s interior ministry, and today commands a 37,000-strong federal police force. The Iraqi interior ministry answers not to the prime minister, but to the Badr hierarchy, led by its leader Hadi al-Ameri, who fought alongside Iranian forces during the Iran-Iraq war. He also now leads the PMF. While the Badr Brigade is the only Iranian proxy that controls an Iraqi ministry, this may not be the case for long.

Iraq’s army is not strong enough to confront these groups. But Sistani has the credibility to lead such an effort. He has long served as a critical check on the power of Iraq’s corrupt ruling elite. After the toppling of Saddam, he ensured that the process of writing a new constitution would be led by an elected assembly, rather than by Washington’s favored Iraqi elites. While he failed to prevent sectarian war, his call for calm, restraint, and unity, helped ensure that the conflict did not transform into a genocide against Sunnis. In August 2014, only two months after his call to arms against ISIS, he forced out then-prime minister Nouri al-Maliki, whose corrupt and authoritarian rule led to the collapse of the Iraqi army.