The story of how the Central Intelligence Agency came to operate a secretive program of rendition, detention, and interrogation under President George W. Bush has been made public by a number of investigations into the abuses that resulted. In 2007, the Red Cross detailed the methods used to interrogate suspects at CIA-run “black sites.” In 2010, the Justice Department’s Office of Professional Responsibility strongly criticized the Bush administration lawyers who wrote the legal memos permitting the CIA to use torture. And last year, the Constitution Project Task Force on Detainee Treatment—a nonpartisan group that included a number of former military and intelligence personnel—analyzed what is known about mistreatment of detainees and the policy decisions that led to such ugly consequences.

Now a new report is expected from the Senate Select Committee on Intelligence, which is charged with overseeing the activities of the CIA. Sen. Dianne Feinstein (D-Calif.), the committee’s chair, launched an investigation into the CIA’s detention and interrogation program in 2009 after learning that the agency had destroyed videotapes of “enhanced interrogations” and had misled Congress about its activities for years. The committee reportedly concluded that the CIA’s use of torture was broader and more brutal than had been acknowledged, and that agents continually lied about the significance of information obtained through torture in order to justify its use. The senators’ report was completed in 2012, but its release has been held up by the CIA’s own “classification review.” Citing security concerns, the agency returned the report’s executive summary with about 15 percent of the text redacted. According to Feinstein—who has long been known as a staunch supporter of the intelligence community—those redactions “eliminate or obscure key facts that support the report’s findings and conclusions.” She asked President Barack Obama to address her concerns, pledging not to release the report summary “until it is readable and understandable.”

It is hard to have faith in the CIA’s judgment about its own secrets, especially given the agency’s recent and flagrant violations of trust. Agents accused intelligence committee members of illegally obtaining an internal agency report, known as the “Panetta review,” that is said to confirm the committee’s findings and contradict the CIA’s official response. Attempting to validate this accusation, CIA personnel illegally searched and read the e-mail of Senate committee members and, when questioned by the agency’s inspector general, “demonstrated a lack of candor about their activities.” After Feinstein decried the intrusion, agency director John O. Brennan expressed outrage at the “spurious allegations.” “My CIA colleagues and I believe strongly in the necessity of effective, strong, and bipartisan congressional oversight,” he insisted.

The CIA’s obstructionism makes a mockery of Brennan’s stated commitment to upholding “the core values that define us as Americans,” not to mention the president’s pledge of “an unprecedented level of openness in government.” On taking office in 2009, Obama declared, “The government should not keep information confidential merely because public officials might be embarrassed by disclosure, because errors and failures might be revealed, or because of speculative or abstract fears.” That, Feinstein and others allege, is precisely the CIA’s motivation for suppressing information in the committee report. As the Constitution Project Task Force found in 2010, “The high level of secrecy surrounding the rendition and torture of detainees since September 11 cannot continue to be justified on the basis of national security.” The price of keeping such secrets, the task force warned, is high: “Ongoing classification of these practices serves only to conceal evidence of wrongdoing and make its repetition more likely.”

Though an intelligence agency operates largely in secret, its credibility depends on respect for the law and clear standards of accountability. Yet, when the CIA breach of Senate computers was confirmed—and Brennan was compelled to apologize—Obama not only voiced “full confidence” in the CIA head, but went on to scold anyone still seeking accountability for torture and other documented human-rights abuses. “It’s important for us not to feel too sanctimonious in retrospect about the tough job that those folks had,” he said, adding that those who tortured “were working hard under enormous pressure and are real patriots.”

The president’s impulse to excuse abuses that occur in the process of preventing terrorism is alarming, given the renewed threat from Islamist extremists in the Middle East. As ISIS continues its campaign of terror in Iraq—making deliberate reference to the CIA’s history of torture—and Obama looks to advisers like Brennan for guidance, careful oversight of the CIA’s counterterrorism activities will be crucial. The Senate intelligence committee is supposed to provide that oversight. But if the CIA can control whether its past transgressions are exposed, then there is no check on its power—and nothing to guarantee that, in the face of new pressure, America’s “core values” will prevail.