Well, the good thing is that Bitcoin doesn't need their permission. Indeed, that is quite the point.
That conversion gets blocked in an entire country/currency and its effectively useless unless you travel.
Grey and black market currencies exist but the exchange rate is very painful. Its mostly only viable when the fiat currency is unstable (or in the black market) for that reason.
Either way, its largely useless in the country it has been grey/black market'd and they are relying on their ability to convert it elsewhere.
Why do that if everyone accepts bitcoin?
And in any case, no you don't. Not as long as cash exists.