Signs of the timesBy David Kravets The Associated Press 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...