UK Prime Minister David Cameron recently announced a plan to restrict access to online pornography. The Daily Mail, which has campaigned for such measures, was quick both to laud and take credit for the initiative. Hot on its heels came calls in the Oireachtas and from the ISPCC for similar moves here.

Almost immediately though, it became apparent that Cameron’s proposals were more more a matter of rhetoric than substance. He announced that ISPs would henceforth block pornographic content by default (this is known as “Default-On” filtering) and that it would be up to individual customers to opt out. In fact what will happen is that customers will be offered a choice as to whether they want to filtering or not, something that some ISPs are already doing. This was quite a feat of spin, taking the opt-in status quo and presenting it as a radical change to opt-out.

It is often the way that bans are easy to demand but difficult or impossible to deliver. These proposals run into trouble when specifics are required. That is why Cameron is already backing off on his big announcement, and why the Icelandic plans for a ban have come to nothing (a member of the parliamentary committee studying the proposal says it has a “near zero” chance of making it to into law).

The problems are both technical and legal. Legally, it has never been easy to define pornography. In 1964, Justice Potter Stewart of the US Supreme Court famously said of defining it “perhaps I could never succeed in intelligibly doing so. But I know it when I see it“. Justice Stewart is no longer with us, so we must do without his guidance. If there’s going to be a law on this, someone will have to sit down and define pornography in a few sentences. Will it include all nudity, or merely all sexually explicit content? What about Page 3? Will text be included as well as images? Where does that leave 50 Shades of Gray? And what of the impending film version of 50 Shades, or other, mainstream films with explicit sexual content? A shorthand for pornography has traditionally been that it was something produced exclusively for the purpose of sexual gratification and lacking artistic merit. I am not sure 50 Shades has much artistic merit, but then who am I to judge? And who is to decide, as a matter of law, what is art and what is not?

If a distinction is to be made between hardcore and softcore pornography, we are into even more subjective territory. Are ISPs to view every piece of sexually explicit material and decide whether it crosses the line or not? They have a hard enough time dealing with child pornography, a real and pressing danger. In Iceland, though specific proposals still have not been made, it was suggested that only violent pornography could be targeted. Which brings us back to 50 Shades again.

On the technical side, the same problem remains. If we have failed over generations to come up with a working definition, then automatic filters have no criteria regarding what to block. The best that can be done is to block certain sites. But with adult material so widely available, there will always be sites that escape the net. Facebook doesn’t allow adult content, but other social networks, like Tumblr and Reddit do. Filters are notoriously inexact. Chances are, if you had family-friendly filters switched on, you would not be able to read this post. Worse, sexual education and information material tends to get blocked too, which is surely a matter of concern when calls for a ban are mostly justified on grounds of child welfare. In any case, as the Minister for Communications, Energy & Natural Resources, Pat Rabbitte pointed out, the EU E-commerce Directive explicitly prohibits (see Article 15) member states from requiring ISPs to monitor content. His recent piece in the Independent opposing such measures is a model of clarity and good sense, when he could easily have score political points by pandering and scare-mongering.

Even where filters are in place, they can be avoided, in the same way as blocked torrent sites can still be accessed. When I was young, the joke amongst the middle-aged was that nobody older than 12 knew how to programme a VCR. Now, with the VCR a relic of the past, the same generation gap exists regarding the internet. You may complacently assume that your computer is locked down. Your teenager may know better.

This, finally, is the nub of them problem. A parent may decide to install content filters on his own computer, accepting that certain unobjectionable material will also be caught in the net. Private households are not required to consider collateral damage to freedom of speech, nor should they be. A society though must give these matters due weight. Minister Rabbitte has made it clear that this is not an area in which the Government wants to get involved. Those calling for a ban might therefore spend their energies more profitably by publicising existing solutions to the problem, and encouraging better parental supervision and understanding of children’s internet use.