Is jail breaking an iPhone 4S illegal?

Is jail breaking an iPhone 4S illegal?

No, if it is your property you can do anything you want with it. If you are only renting/leasing it, then you may violate your rental/lease agreement, which might subject you to some financial obligation.

No. For many years it was considered a grey zone for legality. But then a court ruled that it is legal. The only downside is that if you need tech support then you will have to unjailbreak it before you go to apple and ask for help.

Hope this helped!