In May 2011, the ACLU filed a Freedom of Information Act request with the Justice Department seeking information about the government's use and interpretation of Patriot Act Section 215, which authorizes the government to obtain “any tangible thing” that is “relevant to” a terrorism investigation. Our subsequent FOIA lawsuit to enforce the request compelled the government to release dozens of documents, although many others were withheld from the ACLU and the public. The ACLU continued to fight for additional disclosures concerning the government’s use of Section 215 to secretly collect Americans’ information in bulk, but the district court eventually granted the government’s motion for summary judgment in March 2015.

In 2006, in the first federal challenge ever argued against the NSA's warrantless wiretapping program, the ACLU defeated the Bush administration when a district court declared the program unconstitutional. But in July 2007, the 6th Circuit overturned that decision. The ACLU asked the Supreme Court of the United States to consider the ruling, but in February 2008, the Court declined to review the challenge.

The ACLU of California, the ACLU, Asian Americans Advancing Justice - Asian Law Caucus, and the law firm Bingham McCutchen have filed a lawsuit challenging the federal government's Suspicious Activity Reporting program — a vast expansion of the federal government's domestic intelligence network. The SAR program supposedly facilitates the collection and sharing of information about activity that appears "suspicious," but in practice it targets First Amendment-protected activity, encourages racial and religious profiling, and violates federal law. The plaintiffs are five U.S. citizens whose information has been entered into counterterrorism databases for engaging in lawful conduct, and who have been subject to unwarranted law enforcement and scrutiny. The lawsuit was filed in July 2014 in the U.S. District Court for the Northern District of California. In March 2017, the District Court granted the government’s motion for summary judgment, upholding the SAR program’s standard for data collection. We are appealing that ruling to the Ninth Circuit Court of Appeals.

Government documents obtained by the ACLU show that nationwide programs that collect so-called "Suspicious Activity Reports" provide inadequate privacy safeguards and guidance on the definition of "suspicious activity," leading to violations of Americans' First Amendment and privacy rights, and to racial and religious profiling.

The ACLU has filed Freedom of Information Act (FOIA) requests to learn more about the government’s practice of reading people’s email, text messages, social networking feeds and other private electronic communications without a warrant.