Is Jailbreaking Illegal. Jailbreaking violates copyrights so it is illegal although Apple hardly sues you unless you are. Jailbreaking is not in itself illegal.
Apple seems to me to be coming a far worse monopoly style player than MS. It is not illegal to jailbreak a Fire TV Stick. So it's no surprise that something as innocuous as jailbreaking or rooting is illegal.
When a phone is unlocked, it means that it can work on any mobile network.
Just make sure you receive traces of jailbreaking on your iPhone.
Jailbreaking is not a permanent thing. Library of Congress has ruled that it is now illegal for you to unlock your smartphone if it was. Jailbreaking is not illegal however it will void the warranty of your device.