BRUSSELS—A top European official warned Elon Musk that Twitter Inc. would need to make significant changes to comply with a new European Union law governing social-media platforms and content moderation.
Thierry Breton, the EU’s commissioner for the internal market, held a video call with Mr. Musk on Wednesday to discuss the new legislation, called the Digital Services Act. He said Mr. Musk—who completed his purchase of Twitter in October—stated he planned to get the service ready for the new rules, but Mr. Breton added that more work would be needed.