How would a governmental Bitcoin ban work in practice? How does a potantial Bitcoin ban work in practice in a regime that a.) at least partially allows access to the Internet, and b.) has at least one payment system that is not closely monitored by the government, such as cash.

Some difficulties of enforcing such a ban I can imagine:


Outside exchange access

Although direct access to Bitcoin exchanges behind a nationwide firewall can be restricted (and most likely is), there always exist Tor, proxies, tunnels, VPNs etc. In the extreme case, one could think of using a phone as some sort of acoustic coupler to talk to the outside world, provided there is a counter part of such a tech behind that firewall. Or think of satellite access. Talking to a Bitcoin exchange to obtain coins doesn't require much bandwidth. Paying such an exchange could be an issue if, e.g. the banking system closely monitors all parties involved in credit card transactions. But there may be other ways of paying an outside exchange.

What means could be used to ban access to outside exchanges, and how effective can they be?
Running an exchange inside the country

Obviously such an exchange could only trade coins that are already inside the country if points (1) and (3) cannot be overcome, as far as one can talk about locality of coins in a meaningful sense. Is there anything that could prevent anyone running an exchange by means of splitting the coins already in possession for accepting cash, at an ad hoc spot that frequently changes?
Banning the Bitcoin network itself

Ports can be closed by ISPs etc., but that can be circumvented by simply using ports that must be open (HTTP(S), FTP, IMAP)). As with point (1), there can be simple makeshift ways of obtaining the blockchain from the outside, and transferring blocks with transactions from inside the country back into the blockchain.

As with point (1), what means could be used here, and how effective can they be? Also, how can mining be effectively banned?
Bringing coins into the country

Assuming there are no travel restrictions, so they can go overseas, obtain coins there and bring them into the country, either electronically disguised or encrypted on their devices, or as paper wallets that can easily be hidden.

What systems must be in place to prevent physical import of coins? How useful or practical are physical coins (I know they are not very secure, but that's not the point here), provided they can be inserted into electronic wallets again?
Payment

Obviously, officially registered businesses could not accept Bitcoin (at least not officially), but coins could easily be transferred from person to person once (1) is solved, provided they have the means to setup nodes and inject transactions into the blockchain.

How could a ban private to private even work? Is it even practical to impose such a ban?


It would be great if anyone could answer these questions also in the context of nations that are contentious or outright hostile towards Bitcoin, such as Mainland China, India, Kazakhstan, Bangladesh, Ecuador, Bolivia, Algeria etc.
You may be thinking about this the wrong way.

Most countries have a ban on cars driving above a speed limit. However this is not enforced by using technical means that prevent cars driving over the limit. 

These rules are enforced by doing unpleasant things to people who are detected as having broken the rules.

You may go on to suggest that rules need technical means of detection. But remember that detection need not be perfect. If the consequence of detection is that you lose your job and you life is ruined, few people will take the risk.