Thanks to the internet, many of us now have difficulties distinguishing the public from the private. That applies to teenagers who place intimate details about themselves online; and to spy agencies who snoop on the webcams of hundreds of thousands of unsuspecting users. It appears even our own top judges have trouble telling what's public and what's not. In a staggering judgment delivered late last week, the top court unanimously quashed the conviction of Chan Yau-hei, 26, for posting an inflammatory message in an online forum because the internet is a "medium", not a public or physical space. Most of us would beg to differ. Without their fine legal training, we tend to think that like physical space, online forums are public and our own internet accounts and personal restricted web pages are private. "Publicity" is not restricted by physicality. (I will skip the offending message Chan sent and his target so as not to be sidetracked. I am only interested here in the question of what's public in cyberspace.) According to the judgment, the online act of posting for which Chan was previously convicted for "outraging public decency" is not public. The test of that, write the judges, is that it required the physical presence of at least two other witnesses. Does this mean it's open season to post obscene, inflammatory or threatening messages online, so long as you are alone in your room? It's far from clear from the judgment. There seem to be statutes against those acts, but they are lesser offences than the common law one with which Chan was first charged. The common law offence of outraging public decency, the judges observe, is hundreds of years old, so it constrains them from extending physical or public space to cyberspace. Say what?! You would think given the age of the law written at a time when physical and public space had no cyber connotations, it would be up to the judges, given the famed adaptability and contextualising of British common law, to apply them to a context relevant to our cyberage. As it is, the judges gave a literal interpretation of an old law, and passed on their responsibility to government lawyers to update the statutes and public prosecutors to specify what offensive online messages may be prosecuted.