Former President of Mexico Vicente Fox attends a religious service of the late Lorenzo Zambrano in San Pedro Garza Garcia, on the outskirts of Monterrey May 14, 2014. REUTERS/Daniel Becerril

By Gabriel Stargardter

MEXICO CITY (Reuters) - All drugs including cocaine, heroin and crystal meth will be legal in drug-scarred Mexico within 10 years, former Mexican President Vicente Fox believes, after a court ruling that he said makes the legalization of marijuana inevitable.

"I think marijuana (legalization) is a first step," Fox said in a telephone interview on Tuesday. "It's now irreversible."

Fox was president between 2000 and 2006 and became an advocate of legalizing drugs after leaving office.

Earlier this month, the Supreme Court approved growing marijuana for recreational use. The landmark decision blasts open the door for an eventual legalization in Mexico, where warring gangs have waged a decade of drug violence.

Now that the court has ruled that it is unconstitutional to prevent people from smoking marijuana, Fox said it would eventually have to make a similar decision for drugs like cocaine and heroin.

"The other drugs will take a longer cycle, say five to 10 years," he said.

In a 2013 interview, Fox told Reuters he believed Mexico could legalize pot by the end of current Mexican President Enrique Pena Nieto's six-year term in 2018, which had seemed far-fetched to many at the time, but now appears possible.

Pena Nieto, who has repeatedly said he is against legalization, has called for a national policy debate on the issue of marijuana reform.

Last week, Deputy Interior Minister Roberto Campa, the government official overseeing a review of marijuana policy, said questions such as easing custodial sentences and raising the amount of the drug that people can carry will be considered.

When Fox, a former Coca Cola executive, won the presidency in 2000 as the candidate of the conservative National Action Party (PAN) it ended 71 years of uninterrupted rule by Pena Nieto's Institutional Revolutionary Party (PRI).

Since leaving office, Fox has earned a reputation for speaking his mind and butted heads with the PAN after he voiced support for Pena Nieto in the run-up to the 2012 election, which handed the presidency to the PRI after 12 years of PAN rule.

Nonetheless, his backing of Pena Nieto and his ability to be heard by conservatives on issues they normally chafe at, such as drugs reform, mean many listen when Fox speaks.

Fox said he had no interest in commercializing marijuana himself once legalized but expected major agribusinesses to be interested.

"If they regulate freely so you can produce to export, the big guys are going to jump in," he said, adding that NAFTA-style regulations would be needed if both Mexico and the United States eventually legalize marijuana.

Possessing and consuming tiny amounts of drugs including marijuana and cocaine were decriminalized in Mexico in 2009. The U.S. states of Colorado, Oregon, Washington, Alaska and the District of Columbia have legalized pot use.

But, it is still early days for federal legalization in both countries, Fox said.

"(U.S. President Barack) Obama has to resolve his things over there and Pena Nieto has to make sure he sorts out this problem here," Fox said. "Everything in good time."

Despite holding differing views on marijuana legalization, Fox said he approved of Pena Nieto's strategy against the country's drug gangs, even taking into account this year's high-profile jailbreak of drug kingpin Joaquin "El Chapo" Guzman.

In a tacit swipe at his successor, former PAN President Felipe Calderon, whose military-led assault on the cartels sparked violence that resulted in more than 100,000 drug-related deaths since 2007, Fox said, "(Pena Nieto) doesn't go around putting a military beret on, he's not putting five stars on his chest and he's not conducting a holy war against the cartels."

(Reporting by Gabriel Stargardter; Editing by Simon Gardner, Bill Trott, Toni Reinhold)