Why would legalising drugs put an end to drug cartels? As I said, if drugs were legal, the Gov't would tax them to the hilt, and so the prices would be high. The price of some drugs may go down, but others, that are relatively cheap, would most certainly go up.
Think about it this way: if drugs are legal, then all the people who would already be doing them would continue doing them - one suspects that very few people will be doing drugs simply because they're illegal - but, on top of that, you'll also get people who would've never tried drugs before because they were illegal, and you will also get people doing drugs that wouldn't have even thought about it before.
That means that the demand will rise heavily, this means that the black market would be able to supply the drugs at a lower price now (especially when it would be so much easier to import and illegally manufacture the drugs), many addicts could find themselves turning to the black market, and supporting these cartels all over again.
@Thatmax you're living in a inner-city bubble, it's not as easy to get drugs everywhere, it certainly isn't as easy to get them here. Sure, light drugs (class C & B), are quite easy, but I, and even some of my drug-using friends, wouldn't know where to go for class A drugs.







