A civil liberties panel created in the wake of the 9/11 attacks will announce on Thursday that it thinks the NSA's phone metadata collection — defended as a tool that could have prevented 9/11 — is illegal.

In the wake of those attacks, the 9/11 Commission recommended building an oversight panel to protect civil liberties as the government ramped up its surveillance. It took until 2007 for the the Privacy and Civil Liberties Oversight Board to be created by Congress, and only last year, shortly before the leaks from Edward Snowden began, was it fully staffed. The group, comprised of civilians with diverse backgrounds, will release its report on the NSA at an event in Washington, D.C. on Thursday. The New York Times obtained an advance copy and reports that the group's findings are harsh. Speaking of the most controversial aspect, the bulk collection of phone metadata that the government claims is allowed under Section 215 of the Patriot Act, the report says:

The program “lacks a viable legal foundation under Section 215, implicates constitutional concerns under the First and Fourth Amendments, raises serious threats to privacy and civil liberties as a policy matter, and has shown only limited value,” the report said. “As a result, the board recommends that the government end the program.”

Update, 1:15 p.m.: Here's the panel's full report. White House spokesman Jay Carney told reporters that the president disagrees with its findings.

That finding wasn't unanimous, apparently, with two members of the five-person board dissenting. Both of those who objected to the finding at one point worked as attorneys in the Justice Department under President George W. Bush. One of those two, Elisebeth Cook, writes that even if the phone data collection hasn't prevented terror attacks, it "can allow investigators to 'triage' threats and provide 'peace of mind' if it uncovers no domestic links to a newly discovered terrorism suspect." This is an argument that civil libertarians are unlikely to embrace.

The report will be released less than a week after President Obama announced a series of reforms to the NSA's surveillance tools — ones that don't go as far as Obama's separate review panel (organized by the Director of National Intelligence) recommended and certainly don't suggest that the program is illegal. At the time of Obama's speech, the PCLOB had already announced that its review was impending, and the group briefed Obama on its anticipated findings at the time.

There's not a lot of weight carried by the PCLOB's recommendations from a legal standpoint, but they could be politically significant. Obama left significant parts of the NSA reform efforts to Congress, which already had momentum toward reform. Congressional advocates of the NSA will have to explain to the public why recommendations of a panel created specifically to protect public privacy should be set aside. And even trickier, why a program of data collection that has never stopped an actual terror attack and for which the most common defense is that it could have tracked down 9/11 hijackers — an argument effectively rebutted by The New Yorker — is being rejected by a group that was created specifically to address concerns over September 11th.