Well, there's a few practical problems here.
The internet, by design seems very difficult to police in any meaningful way.
What can you do to someone after all? I mean, it's a big hassle even figuring out what's happened.
If a person tries to rob a bank, everyone at the bank pretty much knows about it. If you try and break into a website, you'd have to be incredibly clumsy indeed for anyone to even know you've done so without them actively looking for someone.
The internet isn't anonymous, but it's a lot more challenging to track down an actual person, and most activities aren't obvious.
Do you know who else is on this website right now? The forum admins probably have an IP log. But the rest of us don't even know if there's another person around.
Now imagine going to a nightclub. You know right away if there are 20 people, or 3000. Some may be trying to hide, but it's not easy to do.
Here, being hidden is the default state, and being visible requires considerable effort.
Furthermore, the internet is, after all, the 'world wide web'. That has implications that are quite pronounced, because that means no one nation has jurisdiction over it.
And, in fact, if you're at all familiar with maritime law, it's surprisingly difficult to enforce anything (even murder and the like) if it's done in international waters.
The internet isn't 'in' any given country, so it's akin to being in international waters.
Combine this with the fact that you have a hard time seeing who else is online, and that it's even more complex than 'international waters', because... Well, for instance:
The Escapist is a US website. It has to obey US law, and if it is punished for anything, the US government is expected to do so in most cases.
I however, am using this site right now, and I'm not a US citizen, not directly subject to any of it's laws, and am directly subject to the laws of my own country.
If you wanted to punish me for doing something illegal on this site, you'd have to contact my government to do so.
Worse still, what's illegal for me, may be different to what's illegal by the laws the website has to obey...
For that matter, this site might potentially contain content that is technically illegal where I live, yet perfectly legal according to the jurisdiction it is in.
Now, if I were to visit the US, I'd be subject to US law. Yet I'm still in my own country, while using a site that in some ways could be considered 'US territory'.
That brings up the problem of me legally speaking being in two places at once, and if they have contradictory laws, you'd have to decide which takes precedence.
The only way in which the internet could be meaningfully policed, is if there was a unified set of laws that were valid worldwide, or all sites were restricted to only those people who were in the same legal jurisdiction as the website...
(Or of course, declaring 'the internet' a seperate country in it's own right. But this would result in much the same problems, since anyone 'on the internet' is still physically in their own country as well. - Not to mention that it seems unlikely you could meaningfully treat the internet as if it were a unified whole.)
It's such a convoluted, impossible mess, because it presents problems that are alien to how the legal system and policing was conceived, and plays havok with the concept of legal jurisdiction, because in practice it makes it possible for a single person to be in multiple places at once, and for all practical intents and purposes completely ignore any kind of border controls.
Yay for being on US property without a visa, or passport, or any legal check whatsoever by the US government... Oh, and as soon as you try and enforce US laws, I'm gone, and you can't touch me without resorting to extradition treaties.
See how messed up that gets when you think about what it implies?