Yes, coca leaves are sold legally and openly in northwest Argentina (the part of the country closest to Peru and Bolivia). The indigenous people have used it for centuries to alleviate problems associated with high altitudes in the Andes. Most of them just put a leaf or two inside the cheek and leave it there to slowly absorb whatever natural chemicals there are in coca. I tried it a couple of times in the northwest (Salta) but never noticed any particular effect. From what I was told in Salta it's legal only in the northwestern provinces where tradition and culture have historically approved of coca use, but it's not legal in Buenos Aires and the rest of the country. Nor is refined cocaine legal anywhere in Argentina.