Slight disagree with the revised analogy.

Imagine you're running this French cum doughnut factory but you only serve local customers. One day a British tourist arrives - "oh I say how delightful!" - and buys, perfectly legally, a cum filled French doughnut. They then take it back to the UK for consumption. Again, the French bakery has broken no laws in France (inserting cum into doughnuts is perfectly legitimate in France). The British tourist broke no laws purchasing the doughnut. But only consumed it back home in Blighty where the government had said that children should be protected from doughnuts filled with cum but for adults it's OK.

It's more obvious in a physical goods scenario where you'd simply say the traveller needs to attest they have the right to the product at the border. Much like a limit on the amount of alcohol that you can bring back from abroad. But it's harder when we're not talking about physical goods, we're talking about information. There isn't an "export license" for information on the internet. Imagine if we had an internet where you couldn't read a newspaper online from Peru because the proprietor didn't purchase any export license. Madness.

The principle should be that countries enforce laws in their own jurisdictions. But the UK wants to additionally enforce it's laws on other jurisdictions. It doesn't want to admit this law is shit. And it doesn't want to block the information as it crosses the border - as in a Great British Firewall like China's. So it has made a pickle all for itself.