The government has imposed many new limits on Americans' legal rights as it fights a war on terror, fundamentally altering the nation's delicate balance between liberty and security.
The changes - including the authority in terror cases to imprison Americans indefinitely, without charges or defense lawyers - substantially expand the government's ability to investigate, arrest, try and detain.
They grant law enforcement easier access to Americans' personal lives while keeping many government operations secret. And the idea that law-abiding citizens can freely associate with other law-abiding citizens without the threat of government surveillance no longer holds.
The Bush administration will not abuse these far-reaching powers, said Viet Dinh, an assistant U.S. attorney general: "I think security exists for liberty to flourish and liberty cannot exist without order and security," Dinh said.
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Still, even supporters are wary.
"One has to pray that those powers are used responsibly," said Charlie Intriago, a former federal prosecutor and money-laundering expert in Miami who said the new provisions could help intercept terrorists' finances.
The USA Patriot Act, hurriedly adopted by Congress and signed by Bush six weeks after the terror attacks, tipped laws in the government's favor in 350 subject areas involving 40 federal agencies.
The Bush administration has since imposed other legal changes without congressional consent, such as allowing federal agents to monitor attorney-client conversations in federal prisons, and encouraging bureaucrats to deny public access to many documents requested under the Freedom of Information Act.
The FBI can monitor political and religious meetings inside the United States now, even when there's no suspicion a crime has been committed - a policy abandoned in the 1970s amid outrage over J. Edgar Hoover's surveillance of the Rev. Martin Luther King Jr. and other activists.
The American Civil Liberties Union, media companies and other organizations are challenging many of the changes, and judges have ruled against the administration in a few early cases. The U.S. Supreme Court has yet to rule on any of the challenges.
"Are we any safer as a nation? I don't know," said Anthony Romero, the ACLU's executive director. "Are we less free? You bet."
In a poll conducted for The Associated Press by ICR/International Communications Research of Media, Pa., 63 percent said they were concerned that the new measures could end up restricting Americans' individual freedoms. Of those, 30 percent of the 1,001 responding adults were "very concerned" and 33 percent "somewhat concerned."
The telephone poll taken Aug. 2-6 has an error margin of 3 percentage points.
"I don't think government should interfere too much in our lives," said Kelly Beaver, 19, a student in North Carolina.
But Arizona caregiver Daniel Martell, 42, said he wasn't concerned at all - "To me, it's not restricting my freedom. There's all kinds of things going on every day to protect freedom."
Americans may never know how valid their concerns are, since everything about terror-related investigations is secret. The administration isn't required to disclose how it is implementing the fundamental changes, making oversight exceedingly difficult.
The Patriot Act allows "black bag" searches for medical and financial records, computer and telephone communications, even for the books Americans borrow from the library.
Judges approve these top-secret warrants in the secret Foreign Intelligence Surveillance Act court. Established to target "foreign powers," FISA now also applies to U.S. citizens, who are no longer protected by the bread-and-butter legal standard of probable cause - prosecutors need only say the search will assist a terror probe.
Dinh credited these changes with reducing the risk of terror, but he wouldn't reveal specifics. "Many of our successes will have to be celebrated in secret," he said.
However, even the FISA court isn't bulletproof. In an opinion announced Aug. 22, FISA judges said the FBI has misled the court 75 times in the past and said the Justice Department has wrongly shared intelligence information with criminal prosecutors who are supposed to meet a tougher standard for evidence.