It seems odd that this was ever required in the first place.

To me, it would make a lot more sense to require any site that could contain adult material (porn, anonymous file upload, file sharing, etc) to add the RTA header [1] to all pages and then put the responsibility on parents to use parental control software to check for the header.

It is trivial to add the header to all modern web servers and load balancers.

In Apache, it looks like this:

    Header always set rating "RTA-5042-1996-1400-1577-RTA"

In HAProxy, it looks like this:

    http-response set-header rating "RTA-5042-1996-1400-1577-RTA"

On a web page, it looks like this:

    <meta name="RATING" content="RTA-5042-1996-1400-1577-RTA" />

[1] - http://www.rtalabel.org/index.php?content=howtofaq