The agency filed the suit Thursday after months of negotiations failed to reach a settlement. Federal officials said that only once before has the DOJ filed a lawsuit against a police department that they were unable to reach an agreement in the last 18 years.
The lawsuit means that a federal judge will decide the escalating standoff with Sheriff Joe Arpaio.
Assistant U.S. Attorney General Thomas Perez said Arpaio and the Maricopa County sheriff's office have been a glaring exception among other cases where the DOJ has been able to work collaboratively with law enforcement agencies.
Arpaio has built his tough reputation on jailing inmates in tents and dressing them in pink underwear. He has aggressively pushed for a stronger role for local police to confront illegal immigration, launching 20 patrols looking for illegal immigrants since January 2008.
The agency first hit Arpaio with allegations in December, saying that a culture of disregard for basic constitutional rights prevailed at the office, which covers metro Phoenix. Talks to reach a settlement broke off last month.
At the time, Arpaio refused to agree to a court-appointed monitor to help enforce a settlement. The sheriff said such an observer would nullify his authority.
After DOJ officials notified Arpaio of the lawsuit, he defended himself at a Wednesday press conference.
"If they sue, we'll go to court," he said. "And then we'll find out the real story. They're telling me how to run my organization. I'd like to get this resolved, but I'm not going to give up my authority to the federal government. It's as simple as that."
In addition to racial profiling, Arpaio's office is accused of punishing Hispanic jail inmates for speaking Spanish and launching some patrols based on complaints about dark-skinned people congregating in a given area or speaking Spanish. A crime was never reported.
The DOJ has been seeking an agreement requiring Arpaio's office to train officers in how to make constitutional traffic stops, collect data on people arrested in traffic stops and assure Latinos that the department is there to also protect them.
The Associated Press contributed to this report.