This bill significantly amends the Immigration and Nationality Act to address United States nationals and naturalized citizens involved in terrorism-related activities. Its primary goal is to establish new grounds for the denaturalization of citizens and the loss of nationality for individuals who support or engage with foreign terrorist organizations. The legislation expands the criteria for denaturalization, making membership in or allegiance to a foreign terrorist organization (FTO) a new basis for revocation of citizenship. Any naturalized person who, after September 30, 1996, commits, conspires to commit, or materially supports an act of terrorism, or provides material support to an FTO, will be deemed to have lacked attachment to the U.S. Constitution at the time of naturalization, leading to citizenship revocation. Regarding the loss of nationality, the bill broadens the activities that constitute renunciation of U.S. citizenship. These include becoming a member of, swearing allegiance to, providing training or material assistance to, or serving in various capacities for an FTO, particularly if the individual knows the FTO will engage in hostilities or commit acts of terror against the U.S. or its nationals. Serving in the military or an armed group of an FTO under certain conditions, such as engaging in hostilities against the U.S. or targeting U.S. nationals, also triggers loss of nationality. The bill also introduces a new ground for deportability for aliens whose naturalization has been revoked or who have relinquished their nationality. It mandates expedited removal proceedings for individuals convicted of terrorism offenses subject to denaturalization, requiring courts to prioritize these cases and creating a rebuttable presumption of deportability. Additionally, the authority for mandatory detention in certain cases is shifted to the Director of U.S. Immigration and Customs Enforcement and the Secretary of Homeland Security.