https://techcrunch.com/2019/04/04/twitter-reverses-stance-and-allows-ad-encouraging-you-to-vote-in-france/

Political ads on social networks have become a lot more complicated in France after the French parliament passed the so-called “fake news law” in late 2018. But the French government didn’t expect Twitter to refuse an ad telling you to register to vote for the European election in May.

Among other things, the fake news law says that you can’t run a political ad without complying to a new set of rules. For instance, social networks have to display who is paying for those campaigns. Social networks also have to say how much money they receive for those campaigns.