“This is unprecedented and highly problematic,” said the report, by the Center on Privacy and Technology at Georgetown’s law school.

Facial recognition technology, long used overseas by the American military and intelligence agencies in Iraq and Afghanistan, is seen by local law enforcement as a tool for identifying criminals, but it has also raised concerns among privacy advocates.

Because African-Americans disproportionately come into contact with, and are arrested by, law enforcement officials, the report said, their police photos will most likely be overrepresented in facial recognition databases.

The authors of the report said the aim was not to stop the use of the software, which they acknowledged had been effective in investigations. Nor did they fault law enforcement officers, who they said “are simply using every tool available to protect the people that they are sworn to serve.”

Rather, they called for Congress and state legislatures to pass laws creating stricter regulations on the technology. Researchers found, for instance, that just one agency — the Ohio Bureau of Criminal Investigation — specifically prohibited using the software to track people engaging in political or religious speech. No state has a law regulating use of the software.