The line between protected criticism and true threats still holds.

The FBI on Thursday arrested Robert Chain in relation to more than a dozen calls to The Boston Globe in August, including death threats over the newspaper’s leadership in calling on newspapers nationwide to speak out against President Trump’s frequent targeting of the media. The FBI found 20 firearms in Mr. Chain’s Encino, Calif., home.

"You're the enemy of the people," Chain told Globe employees on one call, echoing comments from Mr. Trump. He then added, very much on his own, that he would threaten the Globe “as long as you keep attacking the president.”

But as his arrest shows, the system to rein in this sort of threat still is working. “Everyone has a right to express their opinion, but threatening to kill people takes it over the line and will not be tolerated,” said Harold H. Shaw, special agent in charge of the FBI Boston office.

Importantly, it is a Trump administration appointee who is leading the prosecution against Chain – and counseling political temperance. “In a time of increasing political polarization,” said Andrew Lelling, the US attorney in Massachusetts, “and amid the increasing incidence of mass shootings, members of the public must police their own political rhetoric. Or we will.”

Now to our five stories for your Friday, including the last of our Siberian Crossroads series.