A federal judge has ordered that Anthony Levandowski, a former Waymo employee whose autonomous driving startup was acquired by Uber last year, stop working on the ride-hailing company's self-driving car technology.

Why it matters: Barring Levandowski from working on LiDAR technology — which helps cars "see" so they can drive themselves— might not render him entirely useless to Uber, but it certainly makes the $680 million it paid to acquire his startup now seem like too much money.

If Levandowski, his co-founders and their LiDAR technology were the main assets Uber acquired, then it doesn't have much access to them anymore after this ruling, lest it prevails in trial later this year.

The ruling, stemming from Waymo's request for a preliminary injunction to halt Uber's work on self-driving cars, was issued on Thursday evening, but was under seal until now. Levandowski had recently recused himself from working on the technology, but the ruling makes this requirement official.

There's more: Uber is also ordered to return the 14,000 files Levandowski downloaded prior to leaving Waymo, Alphabet's self-driving car unit, to his former employer by May 31. Uber also has to provide a complete timeline of its discussions with him about LiDAR. Levandowski has allegedly made this difficult for Uber by asserting his Fifth Amendment right, something the judge says it could remedy by threatening to fire him if he doesn't turn over the files.