Twitter’s decision to “stop all political advertising on Twitter globally” is a striking one – but how will it decide what is “political”?

If the ad comes from a registered political party or is clearly a campaigning message it might be easy to spot. But it’s not always that simple.

During the 2016 US Presidential election, thousands of ads were placed (mainly on Facebook) by the Russian Internet Research Agency, which the American authorities say was a secretive influence management operation working on behalf of the Putin government.

The IRA was not a registered political party, nor were its adverts overtly political (eg. “vote for this candidate”, “support this policy”). Rather, they tapped into divisive issues in American society such as race and gun control.

Would Twitter have deemed these ads “political”? How will the company make a decision?

Twitter says its ban will include “issue ads”, which its head of legal Vijaya Gadde says are ones “that advocate for or against legislative issues of national importance (such as: climate change, healthcare, immigration, national security, taxes)”.

So could that include the likes of Greenpeace, the Taxpayers’ Alliance and the National Rifle Association? There’s a welter of civic society groups that could be caught up in Twitter’s ban. Its CEO Jack Dorsey says the company will make its policy public on November 15, and it will be interesting to see how it beds in.

As others have pointed out, this could be looked at as a shrewd PR decision by Twitter since it throws the spotlight firmly on Facebook and Google (and its subsidiary YouTube). These two are far bigger players in the advertising world (I was at an online publishers conference yesterday where they were referred to simply as “the duopoly”) and are already facing tough questions about their approach to political ads. If nothing else, Twitter has turned up the heat on a pressing issue.