ACLU sues DOJ to find out more about spy statute

This June 6, 2013 file photo shows the National Security Agency (NSA) campus in Fort Meade, Md. 

AP Photo/Patrick Semansky

The American Civil Liberties Union (ACLU) announced Wednesday that it is suing the Justice Department to obtain more information about one of the government's surveillance programs.

The government only has to tell individuals that it has been spying on them under Section 702 of the Foreign Intelligence Surveillance Act if the evidence gathered is being used in a criminal trial or legal proceeding, the ACLU pointed out in a press release about the lawsuit.

"The vast majority of Americans surveilled under Section 702 will never be criminally prosecuted, so they will never know that the government has been secretly watching them," the ACLU said in its statement Wednesday. "And without definitive proof that the government spied on them, individuals have an incredibly difficult time challenging the government's spying in court."

Under the statute, which is set to expire in December unless Congress renews it, the government sweeps up hundreds of millions of communications -- emails and phone calls -- involving Americans, without a warrant. 

The Justice Department informed the ACLU, in response to another FOIA request, that it had issued a 31-page memo with its new policy, but it only gave the memo to federal prosecutors. The document has not been publicly released. It is this document that the ACLU is suing to release.

CBS News' Paula Reid contributed to this report.