This report discusses the history of constitutional interpretations and legislative responses relevant to the collection of private information for criminal investigation, foreign intelligence gathering, and national security purposes. Next, it summarizes the relevant statutory frameworks and changes made by the USA PATRIOT Act and subsequent measures
Congress enacted the USA PATRIOT Act soon after the 9/11 terrorist attacks. The most controversial sections of the act facilitate the federal government's collection of more information, from a greater number of sources, than had previously been authorized in criminal or foreign intelligence investigations. The Foreign Intelligence Surveillance Act (FISA), the Electronic Communications Privacy Act (ECPA), and the national security letter (NSL) statutes were all bolstered. With the changes came greater access to records showing an individual's spending and communication patterns as well as increased authority to intercept e-mail and telephone conversations and to search homes and businesses. In some cases, evidentiary standards required to obtain court approval for the collection of information were lowered. Other approaches included expanding the scope of information subject to search, adding flexibility to the methods by which information could be collected, and broadening the purposes for which information may be sought.
Some perceived the changes as necessary to unearth terrorist cells and update investigative authorities to respond to the new technologies and characteristics of ever-shifting threats. Others argued that authorities granted by the USA PATRIOT Act and subsequent measures could unnecessarily undermine constitutional rights over time. In response to such concerns, sunset provisions were established for many of the changes.