Places like Egypt, Morocco or Algeria have set bitcoin use, illegal. What exactly stops people that live there to do bitcoin transactions since no one controls the network? And yes, without "cutting" their internet connection.
Preventing people from using Bitcoin at all is impossible because of the very nature of Bitcoin. You cannot exactly ban and block it since it's so decentralized. However, it's quite easy to make sure that people barely use it. If the punishment is too high, the vast majority would not risk it, and thus Bitcoin can be effectively restricted in the country. I don't know what are the laws in these countries and how big of a crime it's there, but I sure would not risk using BTC even if there was a, say $1000 or more fine for that, let alone the serious risk of ending up in prison.