Twitter is finally doing something popular: banning political ads. Yesterday, CEO Jack Dorsey announced that his company will no longer allow sponsored tweets promoting political campaigns. It will also prohibit the much broader category of “issues” ads, with a few exceptions. “This isn’t about free expression. This is about paying for reach,” said Dorsey. “Paying to increase the reach of political speech has significant ramifications that today’s democratic infrastructure may not be prepared to handle.”

The decision was widely supported, according to a survey from consumer polling group CivicScience. But it also sparked immediate debate, confusion, and uncertainty — because Twitter is trying to draw hard policy lines around the nebulous and sometimes all-encompassing realm of politics.

Twitter won’t lay out its new policy until November 15th. But the company already regulates political ads, so it won’t be starting from scratch. In mid-2018, Twitter laid out policies for both direct political campaigning and “issue ads” in the United States. Account holders need to apply for certification, which lets Twitter verify their identities, and their promoted tweets will be specially marked — either with the name of a campaign or with the general label “issue.”

Issue advocacy includes two categories: “ads that refer to an election or a clearly identified candidate” and “ads that advocate for legislative issues of national importance.” Twitter identifies “abortion, healthcare, guns, climate change, immigration, [and] taxes” as examples of legislative issues, although that’s not an exhaustive list.