Previously, Iran made the IRGC's removal from the list a precondition for restoring the multinational deal that limits Iran's nuclear energy program in exchange for sanctions relief. In May, it was reported that Biden decided not to budge on the IRGC designation. 

The Iran nuclear deal—officially, the Joint Comprehensive Plan of Action (JCPOA)—was signed during the Obama administration after lengthy and intense negotiations involving not only the United States and Iran, but also China, France, Germany, Russia and the United Kingdom. It imposed a host of additional restrictions on a nuclear energy program that was already operating under tight International Atomic Energy Agency supervision. 

Though Iran was complying with the deal, Donald Trump—caving to neocon foreign policy advisors and Israel-first mega-donor Sheldon Adelson—unilaterally withdrew the United States from the deal in May 2018. 

Progressing further along a neocon to-do list that also included moving the U.S. embassy from Tel Aviv to Jerusalem, Trump designated the IRGC as a terrorist organization in 2019. In a Hebrew-language tweet, then-Israeli prime minister Benjamin Netanyahu thanked Trump for "acceding to another one of my important requests." 

Lacking any specifics, Trump's designation centered on vague claims that Iran engaged in "malign" behavior in the Middle East and around the world.  

The IRGC is a major Iranian military organization that's independent from the country's regular army. Established in 1979 to safeguard the nascent Islamic republic, it has grown to become the country's dominant military entity—a force of some 125,000 complete with its own army, navy, air force and intelligence service. It also wields political and economic power.