Paul Chambers, 28, will argue the punishment was too severe.

Chambers was convicted of “menace” using microblogging site, Twitter – “a public electronic communications network” – after a security manager at Robin Hood airport in Doncaster saw his Twitter post, according to the judge who sentenced him.

His post said “Robin Hood airport is closed. You’ve got a week and a bit to get your s–t together, otherwise I’m blowing the airport sky high!” according to an article by one of Chambers’ attorneys, David Allen Green, read today at the hearing.

The comment was “a joke aimed at his girlfriend,” another of Chambers’ lawyers, Ben Emmerson said.

“Somebody planning to blow up an airport is hardly likely to post and advertise their intentions on Twitter.”

Chambers was arrested and pursued by the UK Crown Prosecution Service even though airport staff and local police decided the threat wasn’t serious, Green said.

Emmerson said the conviction was “a steamroller to crack a very small nut” and a “disproportionate response to any legitimate public interest.”

Green, whose Twitter handle is @JackofKent, and Guardian reporter, Alan Booth, are tweeting about the hearing as it unfolds, using the hashtag #twitterjoketrial.

Some tweets so far read:

RB: Smith for DPP: “this was not viewed as a joke by those responsible for airport security”
JackofKent: High Court subjecting our submissions on proportionality and Article 10 of ECHR to rigorous and detailed scrutiny.

RB “It is not a question of intent. It is a question of whether it is objectively a menacing message,” says Mr Justice Irwin

RB: Makes “the law looks silly” says Emmerson. “That’s your case,” says Sir Peter Gross. “It is,” agrees Emmerson

Twitter, which has more than 100 million users, is grappling with how to balance freedom of speech and the need to regulate offensive content. The San Francisco-based company said in January it would censor posts on a country-by-country basis rather than globally to address, “different ideas about the contours of freedom of expression.”