I think it is but my understanding is that it is voluntary.
Unfortunately sexual perversion is not always about sexual gratification but power and seeing others suffer. So castration does not always address the issue.
Either way, they should not be allowed out of jail.
The man has proved he will try to circumnavigate any restrictions on his perversions. From moving abroad to accessing the dark web.
As all paedophiles do.
Chop his balls off and throw him down a hole.