[citation][nom]sevenvirtues[/nom]I'm not too sure of consumer laws in america. So someone please correct me if i'm wrong.It I not legal to jailbreak your phone, it is also law that you get a warranty with a product. Therefore apple cannot deny anyone their warranty for jailbreaking.[/citation]
As long as the reason for voiding the warranty is written in the warranty (and it probably is) they can not deny you. However, if there is some clause in the warranty that says, "If you tamper with the phone in any way, you void your warranty" then that is the case. They can not change your service at all though.