In the suit, Waymo, the self-driving car unit of Google parent company Alphabet, accuses Levandowski of stealing 14,000 "highly confidential" files on driverless car technology.
In a strongly worded letter to Levandowski, Uber's head of legal, Salle Yoo, said he needs to return any stolen files or testify under oath that he never took them. And if he doesn't agree, Uber may fire him.
"If you fail to comply in a material manner," Yoo wrote in the letter, written Monday but made public late Thursday, "then Uber will take adverse employment action against you, which may include termination of your employment."
Yoo emphasizes in the letter that Uber is required to take these steps to comply with a court order in the lawsuit.
The legal battle pits two of Silicon Valley's most-watched companies against each other. Between the two, Uber has more to lose. Google has built a massive search business and has its hands in everything from online ad sales to Wi-Fi to social media. Uber, on the other hand, has a more limited business model. It's built a ride-hailing empire, but it's betting on self-driving cars to be the future of its company.
While Waymo's suit focuses on the actions of Levandowski, the case is against Uber. Waymo alleges that Uber colluded with Levandowski to steal designs for its self-driving car tech.
Levandowski used to work at Google but quit in January 2016 to form his own self-driving truck startup, called Otto. Uber bought Otto last August for $680 million and named Levandowski head of its self-driving car program.
Uber has called Waymo's claims "baseless" and argues that its technology is "fundamentally different" from Waymo's.
Complicating matters is the fact that Levandowski has pleaded the Fifth. The US Constitution's Fifth Amendment protects individuals against self-incrimination. This means he's been able to refuse to answer questions about the alleged file theft or turn over his personal laptop.
Uber doesn't dispute that Levandowski downloaded the 14,000 files (though it claims none of those documents entered its servers). Federal Judge William Alsup, who's presiding over the case, agrees with Waymo that something "highly suspicious" happened.
Alsup issued a ruling Monday ordering Uber to return any purloined documents to Waymo by May 31. He also formerly barred Levandowski from working on Uber's lidar, which is the laser technology used in self-driving cars that Levandowski helped pioneer at Google.
"While we have respected your personal liberties, it is our view that the court's order requires us to make these demands of you," Yoo wrote in her letter. "We insist that you do everything in your power to assist us in complying with the order."
Neither Waymo nor a lawyer representing Levandowski responded to a request for comment.
Tech Enabled: CNET chronicles tech's role in providing new kinds of accessibility.
Batteries Not Included: The CNET team reminds us why tech is cool.