The main avenue would be by getting rid of the sanctioned on/off ramps for crypto (that is, crypto exchanges), leaving only the illegal on/off ramps which I'm sure exist.
This obviously wouldn't stop everybody, but it would certainly be a deterrent for all but the most motivated and well-connected of buyers. At that point, exchanging a large amount of crypto would be similar to laundering a large sum of dirty money; possible, but not trivial and certainly not an "easy out" for a major corporation experiencing a ransomware attack.
Laws are how you prevent this.
Can you imagine the Massachusetts Steamship Authority paying in cocaine?
Why would paying in Bitcoin be any different?
Bitcoin is parroted largely by a bunch of libertarian speculative grifters that think they're above the authority of our government to manage the monetary supply. They want to soak up all the advantages of building and controlling an economy.
If you look through the covers, it's all speculation and hype. There's noting "decentralized" or "democratic" about it. Bitcoiners are fine with letting social services and the underserved slip through the cracks as long as they get their reward that they feel they earned.
The US is a democracy, and theoretically it helps people of all backgrounds and socioeconomic statuses. It might not be evenly distributed, but at least we can toss out the bad players. Bitcoin is not a democracy. It rewards the Ponzi schemers at the top and leaves everyone else out to dry.
And now look at what it's gotten us -- unprecedented crime from across international boarders that we can't stop. All brought to you by the remarkable "governmentless decentralization".
Just wait until the kidnappings start. Or the murders for hire.
Fucking good for nothing bitcoin. The world was better before it existed.
Are you seriously using the war on drugs as an example of a successful policy? Drugs are easier to get and more numerous than ever, even though we have these magical laws in place for decades.
What are you basing this on?
From what I've read it seems its only the stupidest of criminals who are using exchanges like Coinbase to cash out, because that's the easiest way to get caught.
Even if cryptocurrency<->fiat transactions continue to be legal in other jurisdictions, making it illegal to trade USD for $crypto would make it very hard for a US company to pay cryptocurrency ransoms making such schemes much less lucrative.
By banning them? In the law? Enforcement would probably pay for itself, plus some. Throw in a whistleblower bonus, like the SEC has, if you want it to run on autopilot.
More aggressive: level repeated 51% attacks. This is well within the budget of any of the G7.
The only way to buy or sell cryptocurrency for the vast majority of people is through exchange companies that have the blessing of the US to continue operating. Even LocalBitcoins goes out of their way to follow KYC laws.
Legal/technical framework is already here.
I think a complete ban on cryptocurrencies is unlikely to succeed, for much the same reasons that the US hasn't banned guns and that the war on drugs is such a shitshow. A punitative tax: 10% of every transaction, for example, would still make cryptocurrencies viable for some extreme schemes, but would make the practice much harder and help establish the "real identity" -> Bitcoin address audit trail. Al Capone was busted on tax evasion, after all.
This is meant sincerely, not glibly: How? How can cryptocurrencies be banned in any meaningful sense?
We can "ban" them in a legal sense ("Use of cryptocurrencies are illegal after 1 Jan 2022"), great. But how can they be practically banned so long as computers themselves are not invaded by governments to observe every detail of their operation and private overlay networks are still technically feasible?