“This is an extensive body of secret law,” the Brennan Center for Justice said of opinions, memos and letters kept secret by the Justice Department, pictured above, and other federal entities. (J. David Ake/AP)

The Justice Department has kept classified at least 74 opinions, memos and letters on national security issues, including interrogation, detention and surveillance, according to a report released Tuesday by the Brennan Center for Justice.

Also still classified are between 25 and 30 significant opinions issued between 2003 and 2013 by the Foreign Intelligence Surveillance Court (FISC), the secretive federal court that interprets the law governing foreign intelligence-gathering inside the United States.

And at the State Department, 807 international agreements signed between 2004 and 2014 have not been published.

Despite President Obama’s pledge to make government more open and transparent, federal agencies are still keeping a considerable amount of policy and legal interpretations under wraps, the Brennan Center found.

The opinions and memos by the Justice Department’s Office of Legal Counsel (OLC) were written between 2002 and 2009, said the report’s author, Elizabeth Goitein, who obtained several data sets through Freedom of Information Act requests.

“This is an extensive body of secret law, which is fundamentally incompatible with democratic self-governance,” said Goitein, the co-director of the Brennan Center’s Liberty and National Security Program. “When the government makes law out of the public eye, the results are more likely to be tainted by bias or groupthink, and are frankly more liable to violate statutes or to be unconstitutional.”

But senior national security officials said the government has in fact been particularly transparent in recent years.

“In the last several years the government has engaged in an unprecedented level of transparency regarding its intelligence collection authorities,” said Brian Hale, a spokesman for the Office of the Director of National Intelligence. Hale said that the transparency includes releasing thousands of pages of documents related to foreign intelligence surveillance on U.S. soil and numerous FISC opinions, including five opinions this year.

The Office of Legal Counsel material that is still secret includes memos documenting advice given over the phone to agencies. They also cover the United States’ response to terrorism, the country’s intelligence activities and international humanitarian law, Justice Department officials said.

Goitein cited as a particularly disturbing example a 2002 OLC memo advising the White House that torturing al-Qaeda terrorists in captivity abroad “may be justified” and that the international laws against torture “may be unconstitutional if applied to interrogations.”

That memo, written by then-OLC head Jay S. Bybee, became public only after it was obtained and published by The Washington Post in 2004. The White House subsequently disavowed the memo.

It is possible that some of the still-classified advice involves little in the way of new legal analysis, but “we have no way of knowing whether that’s the case,” Goitein said. And, she said, “such a large quantity of secret law on these significant topics is inherently problematic.”

Justice Department spokesman Kevin Lewis said the department’s goal is to make OLC opinions available when possible while still protecting classified national security information. “Some opinions may not be appropriate for public release because they could reveal classified national security information or implicate confidential executive branch deliberations,” he said in a statement. “OLC opinions often contain information classified by another agency, and in those circumstances the department typically would not be able to disclose that information unless it was declassified by the originating agency.”

The State Department’s international agreements are binding agreements between nations negotiated by the president under authority delegated by Congress. There is no legislative ratification. Published agreements have dealt with issues such as food safety and commitments to partner with foreign militaries in training exercises.

But 42 percent — almost half — of all international agreements and treaties dating from 2004 to 2014 have not been published. The Case Act of 1972 requires that international agreements be made public, but it allows for certain exemptions, such as for national security purposes.

“The number is pretty stunning if they’re right,” said Oona Hathaway, an international law professor at Yale University and a former national security lawyer in the Defense Department’s Office of General Counsel.

State Department spokesman John Kirby said in a statement that “not every non-publication of an agreement is due to national security purposes.” The law affords multiple exemptions, he noted. He also said that some matters might be the subject of ongoing litigation, which the department cannot comment on.

Between 25 and 30 significant opinions from the Foreign Intelligence Surveillance Court through June 2013 remain classified, the center reported, citing Justice Department data.

“The government,” Hale said, “continues to review for declassification and public release additional older FISC opinions as part of the on-going transparency effort.”

On Wednesday, the American Civil Liberties Union filed a motion in the FISC, seeking the release of all the court’s important, still-classified rulings since Sept. 11, 2001. These opinions cover topics including cellphone location tracking by “Stingray” devices and the government’s use of malware to hack targets’ computers.

After the 2013 disclosures by former National Security Agency contractor Edward Snowden, Congress last year passed the USA Freedom Act, which requires the director of national intelligence to conduct a declassification review of each opinion that includes a significant interpretation of law, and to make the opinion public “to the greatest extent practicable.” At the very least, the intelligence director must make an unclassified summary of the significant interpretation of the law.

All of the significant opinions and orders from June 2015 to the present have been declassified and released pursuant to the new law, according to the national intelligence director’s office.