The American Civil Liberties Union has announced it is suing the US government to put an end to the National Security Agency's blanket collection of communications records, which was exposed last week in the leak of a secret court order demanding the call records and metadata of all Verizon business customers on an "ongoing, daily basis."

The ACLU's is the second legal challenge to surface since multiple disclosures revealed the massive scale of the agency's surveillance activities. The first came from Larry Klayman, a Verizon customer and former chair of government watchdog organization Judicial Watch. The ACLU's lawsuit makes use of the organization's status as a Verizon customer to take aim at the NSA's metadata program, which uses secret interpretations of the Patriot Act's "business records" section to authorize the indiscriminate collection of call logs, geolocation data, and other non-content "telephony metadata" from millions of wireless subscribers inside the US. Statements from officials have also indicated that the program is not limited to Verizon, and has been reauthorized on a recurring three-month basis since 2007.

ACLU deputy legal director Jameel Jaffer calls the program "one of the largest surveillance efforts ever launched by a democratic government against its own citizens," describing its effect as "the equivalent of requiring every American to file a daily report with the government of every location they visited, every person they talked to on the phone, the time of each call, and the length of every conversation." In the complaint, the ACLU claims it has been specifically harmed by the surveillance, because it "gives the government a comprehensive record of our associations and public movements, revealing a wealth of detail about our familial, political, professional, religious and intimate associations," and also "is likely to have a chilling effect on whistle-blowers and others" that might be dissuaded from contacting the organization for legal assistance.

The ACLU's previous NSA lawsuit, from 2008, was dismissed in a 5-4 decision on the grounds that it did not have legal standing to sue, since there was no way to prove it had been targeted. But with the leaked court order clearly showing that Verizon business customers have had their metadata collected, the organization is hoping that will no longer be a problem.

The lawsuit doesn't guarantee a constitutional ruling, however. Previous attempts like Clapper vs Amnesty and Jewel vs NSA have been stonewalled by the US government's repeated invocation of "state secrets," even though the Obama administration had promised to scale back its use of the privilege. The new lawsuit comes that same day that a bipartisan group of senators announced a new bill that would require the government to declassify the secret court rulings which authorize the NSA's warrantless metadata collection.