If you read the link posted elsewhere in the thread by Mathnerd314, it is apparent that the question of whether the states can be sued for copyright infringement is a live one, on which the Supreme Court has just granted certiorari.

Thanks; I was led astray by another case (Cambridge University Press v. Patton) in which a State University was found guilty, but it seems they simply failed to raise the immunity argument and therefore the court didn't apply it.