The reform provides that the Ministry of Health should design and implement public policies to regulate the production, research and medical use of marijuana, and marijuana-based pharmaceutical drugs.
"This means that consumption would no longer be criminalized," Peña Nieto said. But possession of larger amounts would still be punishable under drug trafficking laws.
Some states have made the drug legal for medical purposes; others have removed jail sentences for carrying small amounts; and some let adults 21 and older use it for any reason.
A survey showed 17.2% of middle- and high-school students report having used drugs.
Manuel Mondragón y Kalb, National Commissioner Against Addictions, said that the new limit could be 28 grams (one ounce).
The public hearings will focus on the regulation for self-production and consumption, human rights, the international context, the relation with the anti-crime policy, the prison system and public safety, as well as the medicinal use and commercialization of cannabis and public health.
A legal medical and recreational cannabis market in Mexico could be worth US$1.7 billion a year.
Edgar Valdez Villareal was a top lieutenant and hit man for Arturo Beltrán Leyva and also led a group of killers responsible for murders carried out by the drug trafficking organization.
Wolfgang Götz, director of the European Monitoring Centre for Drugs and Drug Addiction, said that if Mexico legalizes marijuana, it would not solve its main problems, that have to do with crime and heroin and cocaine trafficking.
Colombia joins countries from Mexico to Chile that have experimented with legalization or decriminalization as part of a wave of changing attitudes toward drug use and policies to combat it in Latin America.