Banning... how?
A ban would do serious harm to 2, 3 and 4. If no one could pay legitimately and it would become (ever more) difficult to launder, the ransomware demands would die. The first (connectivity) could be impacted as well. What would happen when traffic shaping makes sync take longer and when every LN transaction risks losing money due to disconnections?
1. Bitcoin transactions don’t require access to the internet at the time the transaction takes place. There have been solutions for performing offline transactions, though none have really taken off. Nevertheless, it’s not hard to do, though it’s riskier for the recipient than an online transaction. I won’t go into the technical details, but it’s nothing fancy. The idea is that you can place money in any number of accounts ahead of time, then simply pay people by handing them the keys to those accounts. There’s little overhead for creating new accounts; often merchants will use a fresh account for every transaction. Of course, the recipient has to be able to trust that they’re actually receiving keys to an account with the right amount of currency, which is a harder problem to solve.
2. This isn’t necessary. Bitcoin was popular in certain criminal communities long before there was any easy way to convert between Bitcoin and fiat. Cashing out dirty Bitcoin to USD remains risky.
3. The UX is already terrible. The UX that criminals experience isn’t the same UX that investors experience. They can’t use services like Coinbase to cash out.
4. Prior to Bitcoin going mainstream, the cover was that you could exchange your Bitcoin for various illegal products and services. (Want to buy a stolen car?) When there’s a whole underground economy whose participants are thoroughly convinced they are outside the reach of the law, any currency will work, as long as there’s a consensus within that community.
Banning cryptocurrency would have some interesting effects, but it would be nearly impossible to enforce, and it wouldn’t have the impact you’re seeking.
This would turn a 'trustless blockchain' to a 'non-blockchain relying on trust'. Assuming this transition can even be done (what would be the point of cryptocurrency in that case?), the result would be like the known hawala networks, which at least do not enable so much criminal activity and have some decent uses.
2,4. Bitcoin had an aura around it. Something experimental not really concerned with money or big crime, maybe a way to buy light drugs. Later on as a magnet for speculation. Remove the official cover, and laundering would become way more difficult.
3. There's terrible UX, and there's 'terrible horrible UX when one could easily lose money because the ISP closes your lightening connection'.
So I think this is possible to enforce, not completely, but there's no need for 100% enforcement to have a positive effect.
You can create the transaction object and hand that over. Transferrable literally as a file.
Instead of having over notes with the private key on them.
Eventually that transaction will need to be settled onchain. This can work in a world without a familiar looking ubiquitous internet. Regional internet cafes or even radio stations can settle signed transactions. People can have stocks of transactions and they just go to the cafe to settle those and also get their updated balance.
This capability always undermines a "ban crypto" thesis, or even a "crypto doesn't survive the apocalypse when the power goes out" thesis. It is merely a concept, just like computers communicating to each other is a replicable concept even if the head of state has an internet kill switch.
Anyway, we don't need a 100% effective ban to get an effect. A 90% ban may well be good enough for any practical purpose. Your example is a good one - sure, there are ways to get around 'internet kill switches' several countries have, but in practice these (unfortunately) work.
The fact that some people in a cafe can get one cryptocurrency transfer going is no defeat for a ban, so long as the ban is effective enough to reach its intended effects (e.g. making ransomware useless).
How would this be done? It only takes a single node capable of connecting to both networks to keep the whole thing working. There are already many nodes working with satellite connections so I'm pretty sure this can't be done even by state actors.
but the utility stays the same at $2.50 or $25,000 (offline-for-most, stateless monetary system with managed/predictable supply)
the same utility is inherited by most of other blockchain technologies
Banning banks from doing business with bitcoin exchanges is not banning bitcoin. Banning use of bitcoin entirely is legally plausible, but technically impossible to implement without draconian internet censorship on the scale of China. It's a 100x harder to ban bitcoin than, say, bittorrent, and banning that in a free society ended up not being possible.
If we can disrupt the network so that even criminals can't get ordinary people to 'pay' via the network, than it's for all practical purposes a ban.
I don't agree that banning it is harder than bittorrent. It's dramatically easier. Bittorrent doesn't have global state, so there's no one place to strike. The entire Bitcoin network depends on global consensus, and therefore there is one place to strike. If it is weakened so that it shrinks enough (how many miners will want to mine for an illegal activity?), than 50%+1 attack will be trivial for a state actor.