A member of my forum posted a link in his signature to an external site, which sold counterfeit dvds, I recieved an email from the copyright holders about this asking for it to be removed, who is responisble the member or the site...I received a warning of them taking it further...
As administrator you should remove the signature link immediatly upon receipt of that warning instead of ask what to do. You are responsible of your forum, unless you have a public statement saying that posters and external links are responsability of the authors.
I would remove the link as it is good practice to let your members know that type of behavior is not permitted and will not be tolerated. It sets a precedence for your site, if you let them get away with it then wrong-doers will walk over you. Your site will continue down a wrong path until they destroy it for everyone, as they will think the site is unmoderated and open-fire! It's best to nip that type of stuff in the bud early on, because spammers/scammers/hackers/etc are like roaches and will spread if you don't do something proactive to thwart it. Additionally, you don't want to waste your time with legal matters, that can hurt you in the long run.
You could remove the link if you feel bad, nobody can force you. You are allowed to link to whoever you want. If that was an issue, google who links to million of illegal things wouldnt do it anymore.
Im going to remove the link that the member posted, it was the threats I didn't like, that and the fact I'm sure they cannot do anything..
They can't do anything really although id be weary on what your hosts policy is v.v anyways removing was probably the best option anyway.