> Laws can't really make anything "structurally impossible"

Require age verification. Kids lie and claim they are 18.

Require better age verification, implemented at the operating system level so that only the parent's administrator account can override it. Kids install a live Linux operating system on a USB drive and boot it, and now they have full access to the web.

Require computers to be cryptographically locked down so that only approved child-protecting operating systems may ever run. For the sake of the kids.

Computing freedom has now been destroyed. It is now structurally impossible for you to be free. It's not your computer anymore, it's the government's, and you better believe they are going to do a lot more than just prevent kids from accessing harmful content.