The group says police need to prove they're not using an FBI counterterrorism task force to spy on peaceful protesters. If police can't provide proof, the ACLU wants the department to withdraw from the task force.
Colorado ACLU legal director Mark Silverstein says his organization obtained FBI documents under the Freedom of Information Act that suggest Denver officers assigned to the Joint Terrorism Task Force might have been gathering information on political activists as recently as December.
That would violate an agreement the city made to settle an ACLU lawsuit over so-called "spy files" police gathered for decades on political activists.
Police agreed not to gather such information unless there was legitimate suspicion of criminal activity.
The agreement calls for periodic reviews to ensure police are complying, but an auditor complained last fall the FBI would not let him talk to Denver officers on the task force or let him see their written reports.
Silverstein said the city must withdraw from the terrorism task force if the FBI does not cooperate with the audits.
Portland, Ore., last month became the first city to end its partnership with the FBI task force, citing concerns similar to the ACLU's.
