“The general rule is, in their individual capacities, members can speak on what the law calls issues of public concern,” Silva said.

But there are special worries for officers who post online and may be grilled by a criminal-defense attorney in court.

“Officers can put themselves in a bad place in terms of their own credibility in terms of providing testimony,” Silva said. “They can create their own impeachment material by going off and pontificating.”

Magnus weighs in occasionally on social media, usually about police issues and occasionally critical of President Trump or his administration. He said officers just need to work to stay within the bounds laid out by the rules.

“I certainly do not share a good many of his views,” Magnus said of Tatum, “but I have to acknowledge that he’s pretty savvy about the way he does it so as not to find himself on the other side of that line.”

On Thursday, Tatum tweeted out an invitation from Alex Jones, host of the conspiracy-mongering InfoWars show, to be interviewed by Jones. To me, accepting an interview with Jones would be crossing the line into behavior that is unacceptable from a known Tucson police officer.