Days after 9/11, the Bush administration, operating under a cloak of secrecy, issued a series of classified memos that claimed unprecedentedly broad authority to use the U.S. military inside the United States in going after terrorists, even claiming that Fourth Amendment protections against unreasonable searches and seizures did not always apply. The long-secret memos, released this week by the Justice Department, shed light on not only the government's immediate response to the 9/11 attacks but its legal basis for seven years of counterterrorism efforts.

For years, the American Civil Liberties Union and other groups have tried to use the courts as a lever to pry loose the legal opinions used to support the government's wiretapping program, its extraordinary rendition of terrorism suspects, and a variety of other post-9/11 efforts aimed at fighting terrorism. But it was the Obama administration's choice to release a handful of memos from the White House Office of Legal Counsel, which issues directives to guide actions of the executive branch.

One memo declared that the military—and, by extension, the president—had nearly unlimited power to act domestically against perceived threats. "We think that the better view is that the Fourth Amendment does not apply to domestic military operations designed to deter and prevent future terrorist attacks," said one opinion from the Office of Legal Counsel dated Oct. 23, 2001. First Amendment rights to free speech and a free press would also "potentially be subordinated to overriding military necessities," according to the memos.

The documents represent a sweeping view of executive power, says Jon Michaels, a professor of national security law at the UCLA School of Law. "Most shocking to me is the extent to which domestic military operations trump the Fourth Amendment," he says.

According to the memo, the U.S. military can be deployed widely inside the country without being subject to constitutional limits, a situation that would deprive citizens of some protections laid out in the Bill of Rights. The military, in the Bush administration's view, had broad legal authority to search and seize documents or persons and property and the authority to keep people under surveillance when it was engaged in counterterrorism operations. Bush's Justice Department also claimed that the U.S. military had the power to intercept Americans' communications without a warrant.

Also contained in the memos was a legal justification for rendering prisoners to countries suspected of torture, despite the provisions of the United Nations Convention Against Torture.

Taken as a whole, the Office of Legal Counsel's opinions asserted that Congress had a subordinate role to that of the president in matters of national security.

In the closing months of the Bush administration, the OLC firmly reversed much of the legal justification for those post-9/11 memos. The outgoing head of the OLC wrote that the opinions were crafted at a unique and unprecedented time. Those opinions "should not be treated as authoritative for any purpose," the OLC stated in October 2008.

Government lawyers concluded that some of the legal rationale for the opinions was doubtful, particularly the interpretation of the Foreign Intelligence Surveillance Act. The OLC further reversed as "unconvincing" the legal basis for opinions issued in 2001 and 2002 that said the president had "unconstrained discretion" to discard obligations enshrined in international treaties.