If you actually read the treaties, while they do set firm limitations on the legal, "non-medical" or "non-scientific" sale of schedule drugs — limits that Uruguay, Colorado and Washington ignored when legalizing cannabis — they don’t otherwise obligate countries to penalize drug use. Even the 1988 convention, the harshest of the three, which instructs countries to criminalize use, still provides an out for states, allowing such laws only as they are "subject to its constitutional principles and the basic concepts of its legal system." This loophole has been used by the Dutch to argue legally for their coffee shops.
Read here the full text of the controversial statements on coca leaf included in this year's Annual Report of the INCB. Some highlights:
> "The Board calls upon the Governments of Bolivia and Peru to initiate action without delay with a view to eliminating uses of coca leaf, including coca leaf chewing" and "each party to the Convention should establish as a criminal offence, when committed intentionally, the possession and purchase of coca leaf for personalconsumption". > "The Board again calls on the Governments of Bolivia and Peru to consider amending their national legislation so as to abolish or prohibit activities that are contrary to the 1961 Convention, such as coca leaf chewing and the manufacture of mate de coca (coca tea)".