[Old Faithful]

Cloning ESNs is a severely punished for the reason that it is used by criminals to get free service and tack on the expense on a victim's account.

On the other hand if you are cloning an ESN from a phone you already own and put out of service, that's another story and your actions may be unethical, but IMO, far from criminal: I doubt reactivating the phone illegally would make a difference for the company that suffered the loss, but, of course, it can be argued otherwise. It's your decision.

If after all that you still feel comfortable with it, do your homework and look it up at the mobile files forum. This is as much as I'm willing to say without risking breaching posting rules and jeopardizing this great forum.