Post-9/11 Legislation Question

In the wake of the September 11, 2001 terrorist attacks in the United States, significant changes occurred in national security policies and perceptions of terrorism. These events not only led to the loss of thousands of lives but also prompted the U.S. government to respond with new measures aimed at preventing future attacks. What legislation was introduced shortly after the 9/11 attacks that aimed to enhance law enforcement's ability to monitor potential terrorist activities?