WaPo oped from Ellen Weintraub, longtime FEC Commissioner:

Would you click on that political ad if you knew it had been generated by a Russian troll farm? Probably not. But without knowing that? Well, you might. Indeed, we now know that millions of people did just that during the 2016 election. How can we prevent a repeat in 2018 and beyond?

For our democracy to work, the American people need to know that the ads they see on their computer screens and in their social media feeds aren’t paid for by Russia or other foreign countries. There’s only one federal agency with the power to stem the flow of foreign money into political ads online: the Federal Election Commission, where I serve as a commissioner. On Thursday, we took a small step forward in that quest, but the news suggests we have much more work to do.

She adds:

Whether Russian bots are engaging in express advocacy (think “Vote for Hillary”), issue advertising (think “Build the wall”) or even disseminating news stories (think “Pizzagate”), if the effort involves any money spent by a foreign national in connection with a U.S. election, it’s in the FEC’s jurisdiction, and it’s illegal.

On the question of issue advocacy paid for by the Russian government, I think the legal issue is far murkier (see fn 74).