It was not clear if other pending terror prosecutions involving metadata evidence would adopt the new legal interpretation.
But the latest efforts in transparency were clouded by the Guardian report on XKeyscore, which it said magnified statements by Snowden that he, as a contractor, could easily access an astonishingly broad menu of personal information on just about anyone.
Security officials had called Snowden's assertion untrue, and White House spokesman Jay Carney echoed that denial on Wednesday by saying allegations of "widespread, unchecked analyst access to NSA collection data are false."
Separately, the NSA said in a statement that its tools include stringent checks to limit what an analyst can do.
"Not every analyst can perform every function and no analyst can operate freely," the statement said.
At the Senate committee hearing, Leahy asked NSA Deputy Director John Inglis whether the agency has held anyone responsible for the Snowden leaks.
"How soon will we know who screwed up?" Leahy asked, contending that inadequate controls allowed the former NSA contractor to leak surveillance program documents to media outlets.
"I think that we'll know over weeks and months precisely what happened and who should then be hold accountable -- and we will hold them accountable," Inglis responded.
House rejects effort to curb NSA phone surveillance
Leahy was impatient with the answer and raised the issue in connection with former Army intelligence analyst Bradley Manning, who was convicted on Tuesday of leaking a trove of Iraq war battlefield reports, diplomatic cables and other information.
"We had a huge security breach, I think we'll all agree, committed by Edward Snowden. And a few years ago Bradley Manning downloaded hundreds of thousands of classified and sensitive documents -- passed them on to WikiLeaks," Leahy said. "Now, if two data breaches of this magnitude occurred in the private sector, somebody would have been held accountable by now."
Snowden has fled the country and remains in diplomatic limbo at the Moscow airport. The United States has charged him with espionage.