A second letter sent Wednesday to congressional leaders urged them to oppose the McConnell bill.
Since mid-2013, the public has urged lawmakers to rein in the NSA surveillance programs, but "Congress has yet to enact meaningful reforms that would end bulk collection, preserve privacy and protect human rights," said the letter, signed by the ACLU, Free Press, the Electronic Frontier Foundation, the Gun Owners of America and conservative think tanks R Street and TechFreedom.
"In the absence of meaningful reform, it is unacceptable to rubber stamp reauthorization of an authority that the government has used to spy on millions of innocent Americans," the letter added.
Supporters of section 215 have long argued it's necessary to help U.S. agencies track down terrorists.
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