The Drug Lords of today exist because of the extraordinary profits resulting from criminalization. Estimates run in the half a trillion range globally per year. By way of comparison there are only twenty or so countries with a national economy of that size.
The situation is exactly analogous to the prohibition era. When gunfights, beatings, murders and firebombs were the business strategy of choice for the pushers of alcohol. Once booze was legalized the bootleggers were immediately driven out of business. Alcohol is heavily taxed today there are however no Bootlegging Lords on the playground pushing cheaper booze on our children.
Nor would such pushers exist for any other drug that we might choose to legalize. Sure the criminals could evade the cost of taxes on their product but there are enormous costs incurred by criminal enterprises that don’t apply to legal ones. This is why marijuana today is sold for hundreds of times what it costs to grow. Our legal producers will not be faced with those costs and so can sell to us below current prices on the street. With profit margins cut to the bone the ‘dread lords and masters’ that control the illegal drug market today will simply melt away like the last snow before the advancing spring.