I'm not somebody who really loves rules and regulations and I'll be the first person to say that America's "war on drugs" has been an utter disaster in multiple ways.
But, generally speaking, flooding a country with cocaine is not what most of us would call beneficial to society.
If you don't think that we should have a society and/or laws, cool, that's another discussion. But if you accept the premise that we should have laws, controlling the flow of industrial quantities of coca leaves seems like the good kind of law.
I mean, I guess we could just let Coca-Cola import metric tons of coca leaves, sell them to whoever the fuck they want, and then just... prosecute the people who do bad things with them? I think we would find that orders of magnitude more work and orders of magnitude less effective. There would be a large cost to society, and nobody wins except Coca-Cola, really.