Far too often, when the ACLU fights for the disclosure of a government record under the Freedom of Information Act, we have a strong feeling that the government isn’t giving us or the court the whole truth. And sometimes, it appears that the government is even being misleading in the details it chooses to leave out. But rarely does a U.S. senator with access to classified information confirm our intuition.

Last year, we filed a FOIA lawsuit for an opinion authored by the Justice Department’s Office of Legal Counsel. The contents of the opinion are mostly a mystery, but we do know that John Yoo wrote the opinion in May 2003, that it relates to the Bush administration’s post-9/11 warrantless wiretapping program, that it is directly relevant to the Cybersecurity Act of 2015 (a bill we opposed and called Patriot Act 2.0), and that it pertains to “common commercial service agreements.”

While these are just a few pieces of the puzzle, they are enough to speculate that the opinion offers a legal interpretation that bears on government relationships with the private sector — likely telecom and internet companies — that enable information sharing and surveillance.

That speculation seems appropriate given how we learned of the opinion in the first place. Sen. Ron Wyden (D-Ore.) has repeatedly warned that the OLC’s opinion on common commercial service agreements is critical to understanding the ongoing cybersecurity debate and contains a legal interpretation that is “inconsistent with the public’s understanding of the law.” Sen. Wyden has a history of alerting the public to the government’s reliance on secret law. The last time the senator warned that the executive branch’s secret legal interpretation would shock the public, it turned out he was referring to the NSA’s unlawful bulk collection of call records under Section 215 of the Patriot Act. The facts underlying his warnings roared into public consciousness with the first Snowden disclosure publicized in June 2013.

The government has withheld the OLC opinion on common commercial service agreements in its entirety and defended that secrecy in court. Last month, after the government filed its brief in our lawsuit, Sen. Wyden wrote a public letter to the attorney general noting that the government’s brief in our case contains a “key assertion” that is “inaccurate” and “central to the DOJ’s legal arguments.” He also attached a classified annex to the letter that discussed this inaccuracy in detail. Senator Wyden then submitted an amicus brief in support of our lawsuit, urging the court to review the classified annex to his public letter. (Five days later, the ACLU filed its brief challenging the government’s suppression of the opinion.)

It is virtually unprecedented for a sitting senator to submit an amicus brief calling out the government for misleading the court. Sen. Wyden’s willingness to do so shows just how important it is to release this OLC opinion. Given his track record and his repeated warnings, the court — and the public — should take notice. The OLC opinion is probably far more meaningful to the public and to our privacy than we could possibly guess.