To my understanding
Bad ESN means registering a handset by a service provider on its network because of Brocken Contract or Stolen.
If that handset is not sold by that service provider (without contact) there will be no problem in switching over to new service provider in the same country or some other country even if they marked as BAD ESN because of non-payment usage charges.
If that handset is sold by a service provider and it is marked as BAD ESN (Brocken Contact) if the same is used with some other service provider in the same country would be illegal.
if that handset is brought to some other country and using with some other service provider amount to illegal but same cannot be taken cognisance by the courts of another country unless the original provider makes a complaint.
Even if there is a complaint raised by the original service provider in their country the same can be executed in our country if there is external treaty between both the countries. There is 2 external treats between USA and India. (Any body wants the entire treaty, contact me I will send hard copy or soft copy.)
In so far as the stolen handsets which were marked as BAD ESN, it is illegal to use/sell in any country including india. So Do not sell BAD ESN (Stolen) handsets in india (broken contract there is risk if there is complaint wants to pursue)
Guru Gopal
Advocate
I will try to answer other types of quires and problems in due course of time.