The bitcoin can be "controlled" not through the mining system but only as a currency. The way may be will the collaboration of all the countries which have regulated it. Later can be added all the other countries which will regulate it (probably all the world). Those can create an Authority which can try to do monetary policies for bitcoin as a currency and to treat it as a world currency. This authority will be independent from every state and will do politics which will have as aim the stability of bitcoin as a currency and the use of it according to the role given to it from those countries. An interesting role of bitcoin it will be this proposition made in this thread: https://bitcointalksearch.org/topic/bitcoin-as-currency-of-currencies-1191118
Comments about this role proposed here are welcomed.
as long as you keep your bitcoins secure yourself, no one, no matter how powerful, can take them from you.
They can try to make all kinds of taxes and regulations, but no one can force you to hand them your bitcoins.
"We know you posess bitcoins, you dog! Give them up or prepare for some extra waterboarding!", they would say.
"I don't have such bitcoins, I told you already. I'm a law abiding citizen. Please let me go!", you would reply.
"Nice try, you miserable rat-dog! We have multiple tips from your neighbors and some informants, you stupid rodent!", they will claim.
"Give us your private keys and we'll let you go!", they would propose.
"Never!", you would say.
Eventually you will die of malnutrition or slave labor or something. If you give them the coins, perhaps you have a chance to be released.