I must not be explaining well, because you're saying the same thing I am. There can be consequences for refusing to comply, ranging from being turned away at the border to being thrown in jail, all the way to, in some countries, torture and execution. That's how the government gets you to comply.
But--here's the critical point--your compliance is required to actually decrypt the email/drive/whatever. This is unlike, say, a cloud hosting provider where the government can just show up with a warrant or probable cause and get the data without your involvement. With strong encryption your data is protected by math, and the math insures that the government or whoever has to go through you to get it. No exceptions. They might throw you in prison for the rest of your life, or threaten to kill your family to get you to give up the encryption keys. But they do need to get you to comply to get access to the decrypted data.
Likewise with blockchain technology. A court or law enforcement agency can't just appropriate stolen bitcoin. They have to either (1) recover the keys, or (2) have the thief pay an equivalent amount in reparations. What I'm saying is that they can't just show up at the Bank of Bitcoin with a warrant and request a stop payment, recovering the funds that way as they're used to with the legacy financial system. The blockchain is irreversible even in the face of the law, for reasons rooted either in physics (proof-of-work) or math (staking).
> The courts will have the power to force blockchains to reverse transactions or other fraud this way - at a technical level still quite difficult but if it becomes law then solutions to make it easier will be created.
No, at a technical level it is impossible. You could no more do this than legislate that pi=3 or raise the speed of light.