UPDATE: On May 30, Customs and Border Protection released the PERF report, along with a revised use-of-force policies manual.

US Customs and Border Protection (CBP) is refusing to release an independent review of its own use-of-force practices, denying repeated requests from members of Congress, media organizations, and civil rights groups.

The review in question was commissioned to the Police Executive Research Forum, a nonprofit that develops best practices for law enforcement agencies. PERF researchers examined sixty-seven use-of-force cases that resulted in nineteen deaths, according to Los Angeles Times, which obtained a leaked version of the “scathing” report earlier this year.

An in-depth investigation by the Arizona Republic found that at least forty-five people have been killed by CBP agents since 2005, including three teenagers who were shot in the back. The Republic‘s investigation also revealed that no agents are known to have been disciplined for any of those incidents.

The Center for Investigative Reporting revealed last Friday that CBP denied its open records request for the PERF report eight months after it was initially filed. In denying the request, CBP personnel cited a Freedom of Information Act exemption intended to protect the “free and frank exchange of information among agency personnel.”

The American Civil Liberties Union filed a lawsuit Thursday seeking to force CBP to release the PERF report, arguing that its disclosure “is critical to a full and fair public debate about CBP’s use-of-force policies and practices.”

According to another document leaked to Los Angeles Times, CBP officials initially rejected two major recommendations from the PERF report: (1) barring agents from shooting at vehicles unless the agents’ lives are at risk and (2) barring agents from shooting at people throwing objects, unless the projectiles are life-threatening. But just two weeks after the LA Times revealed PERF’s recommendations and CBP’s subsequent rejection, Border Patrol Chief Mark J. Fisher ordered agents to stop both practices.

“[R]elease of the PERF Report is necessary to assess why CBP rejected recommendations by the very respected and independent law enforcement think tank whose expertise CBP sought,” the ACLU’s lawsuit states.

Customs and Border Protection ordered the PERF review after a 2012 letter from sixteen members of Congress responding to the death of Anastasio Hernandez Rojas, a migrant who was beaten and tased by border agents in 2010. The circumstances surrounding Rojas’s death were caught on a cell phone video and aired as part of a joint investigation by PBS and The Investigative Fund at The Nation Institute. CBP also commissioned reviews from an internal investigator and the Department of Homeland Security’s Office of the Inspector General.

This post originally appeared at The Nation and is posted here with permission.