Arguing that the CIA has no right to withhold records that are more than 30 years old, a watchdog group filed a motion this week seeking a federal court to compel the spy agency to reveal what it knows about the conservative Catholic group that is the stuff of legend.

Public Citizen is working on behalf of Harry Cason, a Ph.D. student at the City University of New York who filed a Freedom of Information Act (FOIA) to the CIA in 2009 for research he was doing on the U.S. role in Spain’s Franco regime, where Opus Dei allegedly played some part.

But Cason decided to take the CIA to court in January after the agency partially denied his request by releasing more than 200 pages of records but refusing to confirm or deny the existence of other records.

The agency argued that acknowledging the existence of these records would tip the CIA's hand on whether it has information about a covert operation or a confidential source -- information that is not covered under FOIA.

But Public Citizen contended in the motion filed Monday that revealing whether the CIA possesses records which are between 31 and 64 years old would not compromise national security.

"The CIA should not be able to avoid the disclosure requirements of FOIA by making vague appeals to national security, completely divorced from the records requested in this case," said Michael Page, an attorney for Public Citizen who is spearheading the case. "Not only are the records subject to automatic declassification because of their age, but it is implausible that the existence of a half-century-old interest in Opus Dei would undermine national security."

Page added that acknowledging these records would not reveal the CIA's intelligence capabilities.

"Whether the CIA had the ability to monitor Opus Dei before the Internet, cell phones and other modern technologies existed says nothing about the agency's capabilities today," he said.

Opus Dei was portrayed as a murderous, power-hungry cult by author Dan Brown in his bestseller "The Da Vinci Code," which later became a film. The novel asserts that Jesus married Mary Magdalene and had descendants, and that Opus Dei and the Catholic Church were at the center of covering it up.