They can't stop it because anyone can fork bitcoin and create their own digital currency. We could use drugcoin! What they can stop, or make exceedingly difficult, is exchanging state-backed currency to e-coins and vice versa. It's hard enough for some people to get bitcoins. Litecoins introduce an extra step, because most people would have to convert BTC to LTC. But let's admit what this is really about. You want to mine LTC and get free drugs.