Bitcoin has no centre to attack. There is no single organisation or person that controls Bitcoin and transactions don't go through a central clearing house there is really no way a regulator can stop people from downloading Bitcoin wallets and sending each other bitcoins. Government can only use media as a weapon.
Thats so true, and besides bitcoin is the initiative of people who wants a decentralized system away from government control. All the the government can do is to regulate but I doubt if the can regulate 100%.