In the letter, which Breton posted on the social platform formerly known as Twitter, he reminded Musk that he has an obligation to take “very precise” content moderation measures under the European Union’s Digital Services Act and requested a response within 24 hours.

“We have, from qualified sources, reports about potentially illegal content circulating on your service, despite flags from relevant authorities,” Breton wrote in the letter on Tuesday. In particular, violent and terrorist imagery and false and misleading information were circulating without moderation, Breton said. 

Breton cited reports of “fake and manipulated images and facts” on the platform, as well as “repurposed old images of unrelated armed conflict or military footage that actually originated from video games.”

Musk responded with a post on X, saying “everything is open source and transparent, an approach that I know the EU supports” and asking Breton to “list the violations you allude to on X.”

Musk and Breton have developed a rapport over the past year, in part through their shared affection for semiconductors and satellites. Before Musk purchased Twitter, Breton flew to Texas and got the world’s richest man to film an awkward video saying he agreed with the EU’s ideas about content moderation.

Breton paid a visit to X during his tour of Silicon Valley in June and greeted Linda Yaccarino, then less than three weeks on the job as chief executive officer. Musk joined the meeting remotely for a “stress test” of Twitter’s ability to comply with the DSA and assured him at the time that he planned to comply with the laws.