The comedy/magic duo Penn & Teller are part of a group of amici curiae urging the U.S. Court of Appeals for the Third Circuit to reverse a decision by the National Labor Relations Board finding that Ben Domenech, publisher of the online politics and culture website The Federalist, committed an unfair labor practice when he tweeted from his personal Twitter account: “FYI @fdrlst first one of you tries to unionize I swear I’ll send you back to the salt mine.” The Board ordered Domenech to remove the tweet among other penalties.

Amicus curiae means “friend of the court.” People or organizations with a policy interest in a case may file a brief urging the court to rule a certain way. These briefs are in addition to the briefs filed by the parties to the case. In this case Penn & Teller are part of a group who “are committed to preserving free expression and edgy humor. When an obvious joke is misinterpreted as an illegal threat, everyone becomes a little more frightened that the next thing they say might get them haled into court.”

According to the amicus brief, in sanctioning Domenech, the NLRB acted like “a humorless and literal-minded government agenc[y]” that failed to consider the context of the tweet. Domenech has over 80,000 followers. As the brief notes, “[p]eople generally don’t make serious, illegal threats in front of an audience of 83,000 people.”

And the audience was not the only factor. The content of the tweet itself suggested it was a joke. An online publication doesn’t maintain a salt mine. So, in the view of the amicus brief, it was obvious Domenech’s tweet was a joke, not intended to be taken literally. To illustrate its point the brief listed a number of over the top comments, that when read literally, threatened crimes as serious as murder. This included President Obama’s comment to the Jonas Brothers that he had predator drones at his disposal if they came calling on his daughters.

The amicus brief warns of the chilling effect of the NLRB’s ruling: “[f]ailing to understand the type of jokes that are made all the time in freewheeling online discourse is no laughing matter. If a joke about non-existent salt mines performed to 80,000 people can be turned into a federal case, everyone will tweet (and speak) less freely.” It’s an interesting case. And in the NLRB’s defense, even a joke can convey a message. But erring on the side of free expression seems like the way to go here.