What is a Mandamus ? A (writ of) mandamus is an order from a court to an inferior government official ordering the government official to properly fulfill their official duties or correct an abuse of discretion. In case of immigration it deals with asking Courts to intervene when USCIS is not performing its task of adjudicating immigration petition within 180 days of filing date. Congress as part of immigration law has written the law that USCIS should adjudicate petitions at the max period