The Argentinian Supreme Court ruled it unconstitutional to punish people for smoking marijuana as long as they harm no one else.
Combined with Mexico's enactment of laws decriminalizing possession of small quantities of some drugs and Brazil's 2006 decriminalization of consumption, this has the NY Times talking about what it all means:
The new laws and court decisions in the region reflect an urgent desire to reject decades of American prescriptions for distinctly Latin American challenges. Countries in the region are seeking to counteract prison overcrowding, a rise in organized crime and rampant drug violence affecting all levels of society, but in particular the poor and the young.
In February, a commission led by three former Latin American presidents issued a scathing report that condemned Washington’s “war on drugs” as a failure and urged the region to adopt drug policies found in some European countries that focus more on treatment than punishment.
“The global consensus on drug policy is cracking, and an increasing number of countries are agreeing that over-reliance on criminal justice as the ‘solution’ to the drug problem is not helpful at best, and is often harmful,” said Kasia Malinowska-Sempruch, director of the Open Society Institute's Global Drug Policy Program, based in Warsaw, who advocates for treatment for users rather than prison time.