SAN FRANCISCO (AP) — Uber is threatening to fire a key executive accused of stealing self-driving car technology from a Google spin-off unless he waives his constitutional right against self-incrimination so the ride-hailing service can comply with a court order.

The development raises the possibility that Uber may end up dumping Anthony Levandowski, whose expertise in robot-controlled cars is the main reason that the ride-hailing company bought Levandowski’s startup for $680 million nine months ago.

Until last month, Levandowski had been running Uber’s self-driving car division. Although he no longer is doing that, he remains a vital part of Uber’s effort to develop a fleet of robot cars so its service eventually will no longer have to rely on people to pick up passengers.

Waymo, a self-driving car company started by Google, alleges Levandowski downloaded 14,000 documents containing its trade secrets before he founded the startup that he sold to Uber.

Levandowski has asserted his rights under the Fifth Amendment since Waymo filed its lawsuit in February .

But Uber is warning Levandowski that he may lose his job unless he waives those rights and reveals whether he took any Waymo documents. The San Francisco company made the threat in a May 15 letter that became public in a court filing late Thursday.

Any admission by Levandowski that he possesses the Waymo documents could embroil him in even deeper legal trouble. That’s because Waymo’s allegations in the civil case have been referred to the U.S. Attorney’s office in San Francisco for a potential criminal investigation under an unusual order issued last week by U.S. District Judge William Alsup.

Uber had been standing by Levandowski’s right use his Fifth Amendment protections until last week when Alsup issued another decision requiring the company to return any documents belonging to Waymo by May 31.

Alsup wrote that “in complying with this order, Uber has no excuse under the Fifth Amendment to pull any punches as to Levandowski.”

Uber alluded to Alsup’s stern language in its explaining its change of heart to Levandowski.

“While we have respected your personal liberties, it is our view that the court’s order requires us to make these demands of you,” Uber’s general counsel, Salle Yoo, wrote in the letter.

Levandowski is fighting back by trying to persuade Alsup to revise his order to protect his Fifth Amendment rights.

In a filing, Levandowski’s attorneys argued that it’s unconstitutional for a judge to strong-arm an employer into pressuring a worker to give up his Fifth Amendment rights to remain on the job.

“It is an act by the judicial branch of our federal government compelling an individual to choose between preserving his livelihood and preserving his constitutional rights,” Levandowski’s lawyers wrote.

Waymo’s lawsuit already has handcuffed Levandowski. The case prompted Levandowski to temporarily step aside as Uber’s top self-driving car executive and avoid working on anything related to lidar, an array of sensors that enables autonomous vehicles to navigate the roads.

Alsup has ordered Uber to ensure its work on lidar remains off limits to Levandowski.