Argentina and Mexico have taken significant steps towards decriminalising drugs amid a growing Latin American backlash against the US-sponsored "war on drugs".

Argentina's supreme court has ruled it unconstitutional to punish people for using marijuana for personal consumption, an eagerly awaited judgment that gave the government the green light to push for further liberalisation.

It followed Mexico's decision to stop prosecuting people for possession of relatively small quantities of marijuana, cocaine, heroin and other drugs. Instead, they will be referred to clinics and treated as patients, not criminals.