Not ideal. Reuters The UK government plans to censor "non-conventional" pornography — a move that has been criticised by free speech activists, and could see some of the web's most popular sites banned in Britain.

As part of the digital economy bill currently being discussed, the UK government would implement strict porn filters in the UK — forcing sites that host adult content to verify users' ages or risk being blocked in the country.

But the government plans to go further than this, and ban "non-conventional" porn completely, The Guardian reports — a classification that may include everything from female ejaculation to spanking (that leaves marks) and adult material involving urination or menstruation.

So what's going on? Right now, the British Board of Film Classification (BBFC) is responsible for vetting adult content and certifying adult content sold via DVD, and it has strict rules about what's allowed. If it decides the material is unsuitable, it's illegal to sell — even if the acts depicted are totally legal.

As part of the new porn rules, the BBFC will also be responsible for monitoring content online. If it wouldn't be certified for DVD, it won't be certified online, according to The Guardian — and accordingly will be blocked entirely.

These are acts that are perfectly legal for consenting adults to engage in, or for other adults to watch. "It’s mad that we regulate such material that aren’t even criminal acts,” Durham University professor Clare McGlynn told The Guardian. "If we are regulating things like menstrual blood or urination, that’s detracting from a focus on what I think is really the harmful material, and that would be material around child sexual abuse, but also around sexual violence."

It's unclear how this could ever be effectively enforced

The internet is not neatly divided into porn sites and non-porn sites.

It's technically simple to block dedicated fetish websites. But plenty of sites mix porn with non-pornographic content — raising serious questions as to how a ban on "non-conventional" adult content could ever be enforced in practice.

For example:

Reddit lets anyone create new sections (called "subreddits") and is happy to play host to and link out to adult content of all (legal) kinds. (And even popular, nominally non-adult subreddits sometimes play host to adult content.)

Tumblr, the blogging service owned by Yahoo, has a large adult community.

Notorious imageboard 4chan has dedicated porn forums, "work-safe" ones where it is prohibited, and anything-goes sections like its /b/ imageboard, where varied adult and non-adult content can mingle freely.

Even Twitter is much more laissez-faire about adult content than family-friendly Facebook.

These are not small, niche sites. The likes of Reddit and Tumblr have hundreds of millions of users, and anyone can create new sections and communities.

So it's impossible for the companies to know what they are hosting, unless it is reported or brought to their attention — and it'd similarly be impossible for the BBFC to keep an accurate register of all subsections that play host to offending content.

And even if these sites could accurately track any "non-conventional" pornography they host and flag it to British ISPs, it's not clear whether they would: Reddit, for example, has historically taken a fiercely pro-free speech stance.

The British censors would then have to choose between letting huge amounts of content slip through the net, or censoring entirely some of the internet's biggest and most vibrant communities.

Age verification creates additional problems

British Prime Minister Theresa May. Stefan Wermuth/Reuters When it comes to "conventional" adult content that BBFC deems acceptable, sites that host it will be forced to verify Brits' ages before they can access it — or they will be blocked entirely.

Currently, Reddit does not require any form of registration or age checks before accessing adult content; the whole point of 4chan is its totally anonymous and users don't have accounts.

It is questionable whether these sites would make significant structural changes at the behest of British authorities — risking their complete censorship in the country.

As digital rights organisation Open Rights Group also points out, there are significant risks to create registries of Brits who want to look at porn: Recently, "there have been reports of one of the biggest adult websites Adult Friend Finder. Up to 400 million customer logins have been leaked," it wrote. Such info could be highly compromising, putting Brits forced to sign up to porn registries at risk.

No filter will ever be completely effective — as the problems with identifying adult material on community-led sites demonstrates. Technically savvy youths (who the filter is ostensibly intended to protect) will inevitably find ways around it, whether through proxies and VPNs or by tracking down overlooked material. Meanwhile, adults who want to consume legal adult content will have to jump through onerous hurdles and have their choices restricted.

The Digital Economy Bill, currently at the report stage, isn't yet law. It could yet be amended — and anti-censorship activists are furiously pushing for changes. But as it currently stands, it will censor perfectly legal content that depicts no crimes, and casts uncertainty over the status of some the internet's biggest communities.