Nobody. So you don't buy BTC with Bolivars, you sell art commissions or do some work on Mechanical Turk or grind for online game currency with a real market value, and arrange to receive payment in BTC. Then you buy stuff with BTC.
Meanwhile if there isn't that much BTC in the country, that doesn't matter -- currencies can have a different value in different places when arbitrage is restricted. So maybe BTC is worth more there. Or maybe arbitrage isn't really that restricted in practice and if it started to be more expensive there somebody would make a profit by supplying BTC in exchange for exporting boatloads of oil or coffee beans or whatever people in those countries produce.