This isn't a legal principle, it's an assertion. Why is my grant of copyright license revokable? I just can't find comparisons to "permission to trespass" very convincing. (I've also heard things along the lines of "allow people to trespass on your land for long enough and you can no longer prevent it"--some kind of implicit permission--and I'm very sure that has no relation to copyright law.)
Under UK law, you lose title to the land ...There's been a couple of cases in the news recently, and my mother is trying to do exactly that with a bit of land too. That bit may only be 1ft wide by 10ft long, but it's strategically placed where it will cause a lot of nuisance to property speculators...
Cheers, Wol -- Anthony W. Youngman - wol at thewolery dot demon dot co dot uk HEX wondered how much he should tell the Wizards. He felt it would not be a good idea to burden them with too much input. Hex always thought of his reports as Lies-to-People. The Science of Discworld : (c) Terry Pratchett 1999