Conservatives believe government should remain within it's proper function. Stopping dangerous drugs is a proper function of government.
That's certainly arguable, but let's just say, for one moment, that you are correct in that assumption. Seems to me they are not doing a very good job of it. In fact, FedGov sucks in general at any kind of prohibition, apparently. Seems like prohibition only leads to higher crime rates, black markets and promotes general discord. Apparently, you don't care for the rule of law, seeing as how you yourself support black markets and higher crime rates.