A top European Union official warned Elon Musk Friday about his $44 billion purchase of Twitter, telling the wealthiest man in the world he will have to obey the rules.

After a cryptic tweet from Musk hinting he’d completed his acquisition of Twitter, Thierry Breton, the European commissioner for the internal market, warned Musk that he would have to play by the rules, and comply with the bloc’s new digital regulations.

“The bird is freed,” Musk tweeted. In response, Breton quote-tweeted Musk saying: “In Europe, the bird will fly by our rules.”

Although not officially confirmed, a spokesperson for crypto exchange Binance, which provided Musk equity financing for the Twitter takeover, said Friday the transaction had been completed.

Musk, one of Twitter’s most popular users, is known for tweeting everything from announcements about Tesla and his other companies, to memes and attacks on his critics.

The Tesla and SpaceX CEO has previously called himself a “free speech absolutist” and says he wants to reform Twitter as a “digital town square” with less restrictions on what users can share.

Under the European Union’s recently approved Digital Services Act, large tech firms will be obliged to have strong content moderation systems to ensure they can quickly take down illegal material such as hate speech, incitement to terrorism and child sexual abuse.

 For his part, Musk has said he wouldn’t allow illegal content on the platform.

The EU’s rules are expected to come into force by 2024. Companies can be fined up to 6% of global annual revenues for violations.

Guy Verhofstadt, a member of the European Parliament, said Friday that “the need for rules and accountability is bigger than ever.”

“So one man @elonmusk now owns the biggest debate in the world …” he said in a tweet. “Self-regulation in social media has never worked … even with lesser characters than his.”

In May, Musk and Breton met in person, and Musk at the time said the Digital Services Act was “exactly aligned with my thinking.”