Our historical commitment to free speech is put to its greatest test when advocates perceive the most dire threats and resort to the most extreme political rhetoric. The tension between allowing robust political speech while maintaining public safety was perfectly captured by the mistrial declared earlier this month in the federal prosecution in Brooklyn of a right-wing radio personality who, in an Internet blog, seemingly endorsed the killing of three Seventh Circuit judges who had issued a Second Amendment ruling that angered the radio host.

It is well-established that people can be prosecuted for threatening speech, but matters become much murkier when the threats come in the form of political advocacy. Further clouding the picture is the fact that so much extreme political speech, as was true in the Brooklyn case, now appears on the Internet, which makes threats more attenuated but also much more widely circulated.