A top European Union regulator warned billionaire Elon Musk on Tuesday that Twitter will have to comply with the EU’s digital rules under his ownership, complicating Musk’s ambitious free speech agenda.

Musk, who acquired Twitter on Monday for $44 billion after weeks of negotiations, has vowed to overhaul the platform to orient it toward free speech, with significantly less content moderation and censorship, which he has said is the bedrock of a functioning democracy.