> I bet they've already had anti-CSAM blocklists mandated by law

Not just anti-CSAM, the UK has a mandatory "adult content" ISP filter since years (of which you can opt out, through doing so is annoying).

(Which also was used many times already in a inappropriate way by "accidentally" placing websites which are are not adult-only content but politically unpleasant on them because many don't opt out because "it's just for porn/violence right".)

EDIT: Just to be clear the law formulation seems to be over the top/vague and a extremely strict interpretation could imply that ISPs somehow have to block users access to sides even if the user uses an ISP or Tor, so wtf.

The article quotes one of the principals of Andrews & Arnold ISP, which has for a long time traded on providing "real" internet - i.e. unfiltered. Their response to the legal requirement to provide a "filtered" option was a "I want filtering" button on the sign-up page that took you to the results of a Google search for UK ISPs.

As far as I'm aware, complying with this legislation could force A&A to impose filtering on all their users for the first time.

Would certain mailservers become out-of-bounds?

Presumably it would remain possible to ping any IP address, because that doesn't depend on URLs, and the explanatory note seems to say that URL blocking would be sufficient.

Anyway: this kind of nonsense is why I run an Unbound recursive resolver.

they're also dealing with the restrictions on switching fabrics (that were shoe horned in with the 5G hardware restrictions)