Uruguay lashed out at the United Nations, labeling the world body "old school" for its criticism of the country's world-first marijuana law. Global drugs body the International Narcotics Control Board (INCB) warned Uruguay and the US states of Colorado and Washington on Tuesday that legalizing the recreational use of marijuana violated international treaties. In its annual report, the UN agency said it saw a "dangerous" trend in Uruguay after the country approved pioneering legislation legalizing marijuana, becoming the first nation in the world to oversee the production and sale of the drug. Uruguay President Jose Mujica, 78, a leftist and doctor by training, on Wednesday hit back saying: "The United Nations are very old school trying to yank on our ear about this. "Well, we will be paying them just about as much attention as the great powers do when they make decisions regularly" against UN missives, he added. "We are going to win this one, by showing the road to reform," Mujica said. The marijuana law was approved by lawmakers on the initiative of Mujica. It is scheduled to come into practice within weeks, after specific rules and regulations are devised. It authorizes the production, distribution and sale of cannabis, allows individuals to grow their own on a small scale, and creates consumer clubs -- all under state supervision and control. The legalization of marijuana in the largely rural and highly educated South American country of just 3.2 million inhabitants has also drawn the interest of pharmaceutical companies around the world who want to buy the drug for medical uses.