Frank raises a very fair question, to which there is – fortunately or unfortunately, depending on your viewpoint – a fairly unambiguous answer: The question is one of "government action," and the law at present is clear that merely being organized as a corporate entity under the laws of the United States – or otherwise existing "at the beneficence of the national and state governments" – doesn't make a private entity a part of the government (sorry, but I'm at home and don't have the cases handy), any more than does my paying taxes. There may a case to be made that a corporation should be treated differently from a private citizen in this regard, but, except in certain rare circumstances (e.g., the PruneYard case dealt with free speech rights in the public areas – not within the shops themselves – at a large suburban shopping mall, which had essentially taken over the traditional public-meeting-place function of the public town square), the courts haven't done so. The issue comes up quite regularly in the context of gathering signatures on electoral petitions, and the almost-uniform trend is for the court to uphold the private property owner's right to control what gets expressed on private property (surprise), except in the PruneYard-type setting. At least under the First Amendment, and most state constitutions. There may be some states – California, perhaps? – in which the rule under the state constitution is more relaxed in favor of free speech, but it's hard to see a Borders store fitting into that category. This is probably one to take to your state legislators – the Supreme Court is unlikely to agree within our collective lifetimes.

On the other hand, the singer at Borders may have some kind of breach of contract action available (about which I know next to nothing and glad to admit it)

michael