My opinion is that bitcoins are private property and if someone obtains your private key and takes your bitcoins without permission, they are stealing. The problem is getting the authorities to prosecute.
You are right but no one is able to give any punishment to that person because the governments have not approved bitcoin and the other point is that bitcoin is anonymous currency and no one know the owner of addresses.
yes government will not take any action for stealing the private key but i think it is also not good morally and stealing private key of a person is not feeling good.