Milwaukee police have tightened access to their automated license-plate reader system, but the department’s chief of staff warned Tuesday that the changes cannot close every route through which other agencies — including federal immigration authorities — might obtain vehicle data. “There are side doors everywhere,” Milwaukee Police Department Chief of Staff Heather Hough said during a panel discussion at Marquette University Law School. The department recently stopped allowing other law-enforcement agencies to directly access its license-plate reader information. It also limited access within MPD to supervisors, narrowed the investigations in which the technology may be used and reduced the period for retaining images to seven days. The cameras photograph passing vehicles and record information such as license plates, locations and times. Police say the system helps investigators examine serious crimes. But Hough acknowledged that the department’s previous sharing practices could have allowed federal agencies, including U.S. Immigration and Customs Enforcement, to obtain Milwaukee data. She said the risk remains because other police departments and private businesses operate their own camera systems and may share information through contracts with technology companies such as Flock. MPD contracts with three automated license-plate reader vendors, including Flock. Hough said the department’s new restrictions do not eliminate the broader concern that data could move through agencies with different rules. Melinda Brennan, executive director of the ACLU of Wisconsin, said MPD’s new standards were a positive step but questioned why similar protections were not adopted earlier or applied across all law-enforcement agencies. Brennan said license-plate reader networks can enable surveillance without a warrant or probable cause. She cited concerns that the technology could be used to identify people attending protests or traveling across state lines to obtain reproductive health care. She also questioned whether federal authorities had previously obtained access to camera data through other agencies. “The potential for abuse is grave and real,” Brennan said. James Olson, the DeForest police chief and a former MPD officer, said Flock’s marketing helped drive the technology’s spread among law-enforcement agencies in Wisconsin. He described the system as useful, but said DeForest does not operate its own Flock network because of the cost. The Dane County Sheriff’s Office has cameras around DeForest, Olson said, giving the village access to a potential investigative resource without having to build its own network. Olson said departments that use license-plate readers need clear policies, a plan for operating the system and meaningful accountability when officers misuse it. Law-enforcement agencies, he said, operate with the consent of the communities they serve. The discussion reflected a central tension over the technology: Police view searchable vehicle-location information as a tool for solving crimes, while civil-rights advocates warn that interconnected systems can enable widespread tracking of residents’ movements. Milwaukee’s seven-day retention limit and access restrictions reduce the amount of information held by MPD, but they do not govern every database connected to the region’s wider surveillance infrastructure.