lucy24 - 1:31 am on Feb 15, 2013 (gmt 0)
"You may not ...
... copy (whether by printing off onto paper, storing on disk, downloading or in any other way), distribute (including distributing copies), broadcast, alter or tamper with in any way or otherwise use any material contained in the web site except as set out ...
That's not linking. That's an elementary copyright notice.
I suspect that trying to say who and how someone could link to your site would also fall foul of the right to free speech in the USA.
Conversely, your site is perfectly free to deny access to someone from any given referer-- with possible exceptions if your referer blocks are demographically targeted in some illegal way. For example, if your site lists available housing and you block people arriving from sites aimed at a particular ethnic group. I hate to think anyone would be that blatantly stupid, when a simple "It's been rented" or "We've already filled that position" would do. But you never know, do you.
So now we're back at one of the many unanswered questions: Under what circumstances would a real human visitor be unwelcome?
Answer that comes immediately to mind: When the referer is "web-sites-that-you-know-what dot com" or similar, so you know in advance that the visitors are only there to sneer at your site. But that's a pretty small group.