Why it matters: Use of facial recognition software remains a controversial issue, and a new report will likely worsen the public's perception of the technology. According to the Washington Post, both the FBI and Immigration and Customs Enforcement (ICE) have been using photos from Department of Motor Vehicle registries for facial recognition searches, all without the license holders' consent.

Having discovered the information via documents obtained by Georgetown Law researchers, the Post revealed that the agencies used millions of drivers' license photos to create an unofficial surveillance tool.

The system, which has not been authorized by Congress, can be used to track suspected "low-level" criminals along with those who have never committed a crime. House Oversight and Reform Committee Chairman Elijah Cummings (D-Md.) told the Post: "Law enforcement's access of state databases," particularly DMV databases, is "often done in the shadows with no consent."

Texas and Pennsylvania are two of the 21 states that allow the data to be accessed without a court order or a warrant. Washington state is a notable exception, requiring a court order.

With some states allowing undocumented immigrants to obtain drivers' licenses, there's concern that the information they hand over will be used by ICE against them.

Responding to the report, ICE told The Hill: "Due to law-enforcement sensitivities, ICE will not comment on investigative techniques, tactics or tools. During the course of an investigation, ICE has the ability to collaborate with external local, federal and international agencies to obtain information that may assist in case completion and subsequent prosecution. This is an established procedure that is consistent with other law enforcement agencies."

FBI Deputy Assistant Director Kimberly Del Greco said in June that facial recognition helped "preserve" freedoms and security.

Back in May, legislators in San Francisco voted to ban the use of facial recognition technology by government agencies---a first for a US city.