By linking I meant to give exact instructions about how to find a specific page on the site, for a user with enough privilege. It can be a URL, or a demonstration of where you should click, etc.
The site don't have to be open to everyone. But they had no informations about their user's real identity. Everything they could get is at most an "I agree" checkbox during registration.
I'm not asking about whether they can remove the user posting or using the link, but is it possible to legally request removing the link itself (in other sites)?
My first guess is no. I think it is not directly related to copyright as the user didn't post the content, and your terms of service cannot affect other sites. But then I feel there are some quite similar things seemed possible, and someone must be already trying to do this. So is it? If yes, what are those terms called (a part of the copyright license or terms of service, or something else)?
@apsillers pointed out this may have something to do with the contract law. I think indeed this can be done between companies, or companies and employees. But (1) is it still effective if the site just let users to agree to the terms online? (2) If a user did it anyway, I think you can only remove the user in your site, or in theory you can let the user pay. But you still cannot remove things in other sites, because those sites didn't agree to the contract. Is that right?
I'm thinking about a license like this:
- You can use the ideas in whatever way you want (they are not patented; or maybe they are, but the fact your site is describing them cannot be patented).
- You cannot copy the articles directly (there is copyright).
- You cannot refer to the explanations in this site in formal documents of a company, or prove this site has promoted this idea. Or a weaker term: you have to pay to do that.
- You can rewrite the whole things, or don't leave explanations, or whatever.
This is indeed a bad idea which I thought it must be disallowed at first. But it seemed to be weaker than what a company can have with their employees.