Attorneys for the American Civil Liberties Union appeared in U.S. District Court Friday to argue for a preliminary injunction that would halt the National Security Agency's collection of all Americans' phone records.

Judge William Pauley did not set a time frame for when he might announce his decision – but as he reviews the case, NSA opponents may have cause for optimism.

ACLU legal fellow Brett Max Kaufman, one of the attorneys in court for the hearing, said Pauley seemed skeptical of the government's reliance on the Supreme Court's 1979 Smith v. Maryland decision.

The landmark ruling found a criminal defendant did not have a reasonable expectation of privacy over a list of phone numbers he dialed within a two-day period. The ruling is a key pillar of the government's legal argument for the surveillance program.

"Judge Pauley asked some very skeptical questions about the lasting value of Smith v. Maryland with respect to a program as vast as this," Kaufman said.

Another federal judge mulling the NSA phone-record collection also seems skeptical of the case's relevance.

U.S. District Court Judge Richard Leon said Monday during a preliminary injunction hearing in Washington, D.C., that the influence of Smith v. Maryland "may be very limited" because "the technology that was being used in that case... paled in comparison to the technology the NSA has at its disposal."

Leon suggested the Supreme Court's 2012 U.S. v. Jones decision, which imposed limits on police use of GPS tracking, was a more relevant legal barometer.

— ACLU National (@ACLU) November 22, 2013

"Both Judge Leon and Judge Pauley today in New York really did press the government on whether Smith v. Maryland really says all the government says it does," Kaufman said. "With respect to the Fourth Amendment claim of both the ACLU plaintiffs and Mr. Klayman, Smith is the primary defense of the government and it is the main case the government relies on.

"It was very clear that [Pauley] shared the skepticism of Judge Leon as to whether Smith controls the situation here," he observed.

As with Leon, Pauley invoked U.S. v. Jones, according to Kaufman.

"Judge Pauley asked some very sharp questions," he said. "He did question [government lawyers] about the meaning of Jones and even referred to the various opinions in Jones. He was clearly steeped in this area of the law."

The ACLU's lawsuit argues the government lacks authority under Section 215 of the Patriot Act for the dragnet collection of phone metadata. The civil liberties group filed its lawsuit against the program in June, when The Guardian published a secret Foreign Intelligence Surveillance Court order that compelled Verizon to hand over the information.

The FISC secretly authorized the record collection citing Section 215 of the Patriot Act for seven years before whistle-blower Edward Snowden handed classified information exposing the collection to the media. After the leaks, Patriot Act author Rep. Jim Sensenbrenner, R-Wis., said the phone program's scope – in his opinion – was not authorized by the law.

Unlike the case heard by Leon in Washington, D.C., which is brought by former Reagan prosecutor Larry Klayman, the ACLU says there's no issue of standing in its challenge. That's because the ACLU is a customer of the Verizon entity named in the leaked FISC order, whereas Klayman and his clients are Verizon Wireless customers.

Leon wrestled Monday with whether he has the authority to overrule the FISC, but Kaufman says that angst was largely absent from Pauley's courtroom - possibly because the Department of Justice suggested that venue in arguments submitted to the Supreme Court against a lawsuit from the Electronic Privacy Information Center. The Supreme Court declined to consider that suit Monday.