The opium trade and coca trade have been greatly hindered by international efforts to maintain management and further international models of success for rehabilitation, combating, and prevention are all sensible avenues to undertake. The more humans work together on any level the easier, smarter, and more manageable the systems we function in.
Domestic drug policy should remain in the purview of individual countries. International law should be used solely for global environmental concerns (i.E. Pollution that crosses borders, greenhouse gas emissions), disputes between nations, and human rights concerns.
Drug policy should be entirely up to the individual country.
If anything is left in international law it should be an agreement to cooperate with other countries to go after people who are involved in the illegal drug trade within those other countries even if those drugs happen to be legal in the country they fled to. Each country should be allowed to determine what is legal and what is not within its own borders.
International law should with the exceptions of human rights concerns have nothing to do with domestic policy. Otherwise countries are not truly sovereign.
In my own opinion, the United States should withdrawl from the UN and concentrate on our own domestic problems, which are increasing in number on a weekly basis. We're being overrun by illegals flooding our southern borders, our police look more like Afghanistan patrols than they do local police departments, the public assistance rolls grow as decent job opportunities disappear.
We have ZERO business telling other countries how they should conduct business, and the US Constitution certainly isn't up for debate, either.