I have written this piece for Slate. It begins:

Robert Mueller let Donald Trump Jr. off the hook too easily for potential campaign finance violations that arose from the June 2016 meeting in Trump Tower with Russian operatives. Mueller’s questionable exercise of prosecutorial discretion is bad news for how campaigns and foreign entities might conduct themselves in the runup to the 2020 elections.

Like many others, I am still poring over Mueller’s 448-page partially redacted report. My initial general impression of Volume 1—the part dealing with Russian interference in the 2016 elections and the connections between Trump—is that Mueller and his team did a thorough and fair job in investigating what happened and in describing the facts. But on the potential campaign finance violations, Mueller fell short in numerous ways…..

I’m afraid that this flagging of the issue does more harm than good. Mueller has now given campaigns credible reason to believe they can accept help from foreign governments because they may have a constitutional right to do so. That’s even more troubling for what it says about 2020 than what it says about 2016.