A court filing by federal prosecutors provides detail on the role of Mousa Abu Marzook as a leader of the United States-based Muslim Brotherhood and Palestine Committee:
By the outbreak of the First Intifada, the Muslim Brotherhood in the United States was significant and well organized. In 1987, the governing body of the International Muslim Brotherhood decided to focus its mission on the Palestinian issue, and directed that Palestine Committees be formed in countries throughout the world. In the United States, the Palestine Committee was comprised of active Muslim Brotherhood members of Palestinian origin. The leader of the Palestinian Committee in the United States at that time was unindicted co-conspirator Mousa Abu Marzook. Marzook is now – and has been since 1995 – a Specially Designated Terrorist and Hamas leader. In fact, in the early 1990s, Marzook left his post as a leader of the United States-based Muslim Brotherhood and Palestinian Committee to take over as Hamas’ Political Bureau Chief, the organization’s highest official position. The creation and growth of the Palestine Committee in the United States are evidenced in part by documents that the government seized in 2004 from the Virginia home of unindicted co-conspirator and Palestinian Committee member Ismail Elbarasse. As shown by those documents and other evidence, the Muslim Brotherhood directed its Palestinian Committees throughout the world, including the United States, to carry out the mandate of assisting Sheik Yassin and his newly-formed Hamas Movement. In accordance with that mandate, the Palestinian Committee in the United States, which included the defendants Elashi, Baker and El-Mezain, oversaw a number of sub- organizations charged with varying missions calculated to comprehensively address Hamas’ needs. These organizations included the United Association for Studies and Research (UASR) (“think tank”), the Islamic Association of Palestine (IAP) (propaganda and information) and the Occupied Land Fund (OLF) (money), later to become the defendant HLF. The defendant Shukri Abu Baker was in charge of the HLF and, along with the defendants El-Mezain and Elashi, set out to establish what would become the highest grossing Islamic charity in the United States.
It should be noted that the Council on American Islamic Relations (CAIR) grew directly out of the IAP and Hamas infrastructure in the U.S.