WASHINGTON — Sen. Ron Wyden, D-Ore., promised Wednesday to keep challenging the Obama administration to release its undisclosed legal interpretations of U.S. laws, including those that shape its policy toward using drones for targeted killings.

“I believe the Congress and the public have to insist that the executive branch’s official interpretation of the law be publicly known,” he said. “I’ve got a lot more to do in terms of just staying at it.”

For two years, Wyden has conducted a crusade to get the administration to provide legal memos written by the Justice Department’s Office of Legal Counsel related to U.S. drone policy. Earlier this month, the administration turned the memos over to members of the Senate Intelligence Committee after Wyden threatened to block the confirmation of White House counterterrorism adviser John Brennan as head of the CIA.

The issues surrounding the administration’s drone policy gained more visibility after Sen. Rand Paul, R-Ky., staged a 13-hour talking filibuster last week until the White House divulged whether it believes it has the authority to target a noncombatant U.S. citizen on American soil.

He relented after Attorney General Eric Holder said in a letter that the answer is “No.”

Wyden was the only Democratic senator who participated in Paul’s filibuster.

“I think this debate is just beginning,” Wyden said Wednesday. Once he has had time to review the OLC memos more thoroughly, he will have more to say about their content, he said.

Wyden’s remarks came at an event sponsored by Citizens for Responsibility and Ethics in Washington titled “OLC Memoranda: Does U.S. Secret Law Threaten Our Democracy?” The event was part of Sunshine Week, a week dedicated to highlighting transparency (or lack thereof) in government.

Wyden introduced a panel that included New York Times reporter Charlie Savage, who has sued the Obama administration under the Freedom of Information Act after the government refused to disclose the OLC memos, and Jameel Jaffer, deputy legal director of the American Civil Liberties Union, which has also sued the administration for disclosure of information surrounding its drone policies.

The government often has legitimate reasons for withholding information from the public, Wyden said, and he is not asking it to reveal operational information that would compromise national security or put the lives of intelligence operatives at risk. But secret operations are different from secret law, he said.

“Our laws, which are public, are secretly reinterpreted behind closed doors by a small number of government officials without public scrutiny. When that kind of thing happens, you are more likely to end up with the government interpreting the law in ways that the American people will be, in many instances, reluctant to accept,” he said.

For example, the George W. Bush administration approved torture and warrantless wiretap programs without public debate or input, he said. The Bush administration’s OLC memos justifying torture remained secret until they were released by the Obama administration in 2009.

“If the (U.S.) Forest Service interprets a law in an unusual way, it is likely to become public very quickly. If the CIA or (National Security Agency) interprets a law in an unusual fashion, it might well stay secret for years. That is what has happened in the past,” he said. “Much of that narrative involves government officials secretly deciding that the law didn’t mean what most people thought it meant.”

Wyden said he has used public hearings, including Brennan’s confirmation hearing last month, to try to slowly expand what the public knows about secret law.

Wyden asked Brennan to define the evidentiary standard required before the administration can authorize lethal force, if an American citizen must be given the chance to surrender before he or she is targeted, and in which countries the U.S. has conducted drone strikes.

“I thought his answers were exceptionally vague,” Wyden said.

At least three U.S. citizens were killed in drone strikes in Yemen in 2011, although The New York Times reported that only one, Anwar al-Awlaki, was specifically targeted.

Samir Kahn, a magazine editor from North Carolina, was inadvertently killed in the strike that killedal-Awlaki, and two weeks later, al-Awlaki’s 16-year-old son Abdulrahman was also killed.

Jaffer said that the ACLU believes that once the OLC’s confidential advice had been put into practice, it had been adopted as policy, and is no longer withholdable from the public.

“I don’t think we should be too quick to accept the government’s distinction between legal counsel on one hand and operational information on the other hand, in part because the government takes a very broad view of what counts as operational information,” he said. “Sometimes, the public interest in disclosure of operational information is pretty significant.”

The government has disclosed operational information about the May 2011 raid that killed Osama Bin Laden because it recognizes the public’s right to know more about the death of the man behind the 9/11 attacks, he said.

It can also be hard to separate operational information from the legal justification in the memos, said Savage. As modern intelligence relies more on computerized technology and electronic surveillance, it has become easier to “reverse engineer” legal opinions about the extent of the government’s authority to conduct certain activities and figure out what the intelligence community wants to do, he said.