Los Angeles bans sale of medicinal marijuana
15 August 2012 Last updated at 17:37 BST
California legalised medical marijuana in 1996 but since then authorities think the use of the drug has spiralled out of control.
They are worried that young people have too easy access to the drug and are illegally using it for recreational purposes, in turn leading to an increase in crime in areas where it is for sale.
BBC Mundo's Valeria Perasso reports.