At his first inauguration, Barack Obama rejected “as false the choice between our safety and our ideals.” On his second day in office, he announced plans to close the Guantánamo detention facility within a year and to end immediately George W. Bush’s authorization of the use of “enhanced interrogation techniques,” a euphemism for torture.

Sadly, those steps in January 2009 turned out to be the high points of Obama’s determination to end Bush’s trampling of basic rights in the name of fighting terrorism. Whether the issue is torture, Guantánamo, military commissions, drone attacks, or electronic surveillance, Obama’s tenure has been one of disappointment for those who had hoped for a more consistently rights-respecting approach to combating terrorism.

Torture, paradoxically, has been the area where Obama’s policy has been both the firmest and the most qualified. By all available evidence, use of the “enhanced interrogation techniques” has stopped. Obama also prohibited further use of secret detention facilities where suspects had “disappeared” in CIA custody for torture. (To be fair, Bush by the end of his presidency seemed to have ended both too.)

However, the Convention against Torture, which the United States ratified in 1994, not only prohibits torture and other mistreatment but also requires that it be investigated and punished. On this latter obligation, Obama has utterly failed. The Obama Justice Department has not prosecuted anyone for Bush-era torture. It has conducted only a narrowly focused investigation into interrogation techniques that exceeded those authorized by Bush’s Justice Department, and that investigation yielded no prosecutions.

It was left to Congress, most notably the Senate Select Committee on Intelligence under the chairmanship of Senator Dianne Feinstein of California, to conduct a more comprehensive investigation. In December, it released a 528-page summary of a 6,700-page report on the CIA’s Bush-era torture.

A principal finding of the report is that the “CIA’s use of its enhanced interrogation techniques was not an effective means of acquiring intelligence or gaining cooperation from detainees.” It is sad that we must even debate the efficacy of torture, given that the legal and moral prohibition of torture is among the strongest we have. The Geneva Conventions, for example, forbid it even in time of war. But when facing a serious security threat, as the United States did after the September 11, 2001, attacks, it can be tempting to rationalize the illegal and immoral as necessary, so this finding that torture was ineffective matters.

The CIA challenges this conclusion. While acknowledging that mistakes were made, it insists that “enhanced interrogation techniques,” which the Senate report shows to have been far more brutal than previously thought, did produce actionable intelligence. Yet it should give us pause that Democratic and Republican senators who have studied the report conclude that torture was ineffective, while the…