Simple; you force ISPs to block any incoming connections to services/machines that don't have the proper governmental license. Any servers that allow two client nodes to communicate freely (like a proxy, or VPN) won't get a license.
To prevent smartasses from using servers in countries without these restrictions, you further force ISPs to prevent any large amounts of data from being uploaded to those countries (cumulative, to avoid tricks like uploading small parts to many servers). E.g. back in the early 00s, some of our ISPs used to have different traffic caps for national vs international connections, here in Portugal.
It's not that hard if you're willing to go the full mile.
There's still peer to peer networks (see firechat and hong kong protests), there's still the whole field of steganography (hide data in pictures of cats for example), finally, there's still offline transport. (usb sticks with copies of wikipedia in Cuba for example)
That would be one strategy for making the next generation of kids experts in networking, but for the scheme to work you would be putting whatever lame ass the government can hire to implement the system against every hacker in that country. The government would have to win every time, the hacker only once - and he would instantly get respect and social standing in his circles.
Even that wouldn't really stomp out filesharing, local groups and p2p networks would crop up. The genie is out of its bottle and I'm skeptical that it can ever be put back inside.
To prevent smartasses from using servers in countries without these restrictions, you further force ISPs to prevent any large amounts of data from being uploaded to those countries (cumulative, to avoid tricks like uploading small parts to many servers). E.g. back in the early 00s, some of our ISPs used to have different traffic caps for national vs international connections, here in Portugal.
It's not that hard if you're willing to go the full mile.