Encryption for end users is de facto legal almost everywhere except for UK. For vendors it's illegal almost everywhere maybe except for USA, but that's just how the law works in USA: you receive a subpoena, then it's up to your luck.
If you think about it, it's more or less the only way this could work in any democratic society.
https://www.theregister.com/2025/02/26/signal_will_withdraw_...
Encryption is legal in the UK.
But if the government turns up asking for your decryption keys, "you can't have them" is not an option unless you wish to enjoy the luxurious surrounds of a prison cell until you change your mind.
Which, to be fair, is basically the case worldwide, as per the famous XKCD cartoon[1].
If you don’t have they keys, you can’t hand them over, for one thing.
Also, the wrench treatment is extremely unlikely in most democracies. Now, deplatforming such as seizure of DNS names and such, is another matter and varies, often orthogonally to the risk of wrench treatment.
If you prefer ... substitute "wrench treatment" for the democratic wording: "jail time and the associated criminal prosecution process"
We're talking about "if the government turns up asking for your decryption keys, ...".
> Where has this happened?
Pretty much everywhere. Even in the US you can only avoid it if you're careful; if you admit to knowing the keys then you can't. Either way you're dealing with the "criminal prosecution process" as GP pointed out.
The trouble with deniable encryption is its viable use-case is very narrow.
It is, for example, not viable to use deniable encryption when exchanging messages with others.
If the authorities, through whatever means, get the a copy of an encrypted message you sent, and they have done sufficient metadata homework to link it back to you, find your address and come knock on your door, then you are going to seriously struggle with a deniable encryption defence.