The goal was to curb production of methamphetamine by cutting off key ingredients. It worked: Domestic production of methamphetamine fell. But a blow to meth labs in the United States became, in turn, a boon to a group in Mexico.

La Familia started manufacturing meth a few years earlier in the western state of Michoacán. By 2006, the group had emerged as a major distributor.

No one claims that the emergence of La Familia was the direct result of the US law. But US production of meth has decreased dramatically since 2004, according to the National Drug Intelligence Center's National Methamphetamine Threat Asses­sment of 2008.

A global report from the United Nations Office on Drugs and Crime from 2008 also shows a 92 percent decline in the number of large-capacity labs in the US from 2001 to 2007. But in the same period, methamphetamine seized along the Mexican border dramatically increased. (There was a significant dip again in 2007, but seizure numbers are still higher than they were in 2001.)

Experts say that the expansion of meth networks operated by Mexican organizations is a major factor in the sustained meth supplies in the US today, even with new import restrictions on chemicals in Mexico.

Some are not surprised.

"The entire history of US interdiction policies toward Latin America in the 20th century has created that pattern. The inadvertent [results] of crackdowns or interdiction policies in the Andes, and in the Caribbean, have always had enormously adverse effects," says Paul Gootenberg, a history professor at the State University of New York, Stony Brook, and the author of "Andean Cocaine: The Making of a Global Drug."

Even meth's surging popularity was in part created by the crackdown on cocaine. In other words, he says, this is an old story about unintended consequences.

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The rise of La Famalia, a narco-evangelist cartel