And how would you do that?

There are times when I think that power or the thought of power goes to some peoples heads. Either that or they think they have a good idea and want to try and force someone else to comply with it, even when that someone else isn't under their power or jurisdiction.
BBC.

A UK industry regulator has called for the law to be changed to require pornography sites to carry out age checks before granting access.
Video-on-demand watchdog Atvod said the government must act to protect children from seeing graphic adult material.
It said credit and debit card operators would be forbidden from processing payments from British customers to sites that did not comply.
But one campaigner said the action would be a "worthless gesture".

OK, first things first, credit and debit card operators may not know (or care) if the site is a porn one, the porn industry were the ones who drove the initial payment online security issues in the first place and would appear to be past masters in the plain brown package approach of using innocuous names on a bill to avoid raised eyebrows from potentially offended partners.
Second, who the hell are these people who think that they have the right to tell other who or what we can spend our money on if it isn't a crime in the first place?
Thirdly, you don't need a credit card to access porn, the internet is bloody inundated with sites that are free and do not require a credit card.
Again and again it all for the children whilst forgetting that the biggest tool to keeping kids away from images that parents don't want seen are actually the parents themselves who can if they wish set up censoring and filtering on their own access points to prevent kids from seeing stuff.
This is simply a pointless gesture by someone who wants a few headlines on the forthcoming paedogeddon if we don't do as they say (and pretty much not as they do)