Nonetheless, the prospect of U.S. involvement in surveillance could be extremely sensitive in Mexico, where the United States historically has been viewed by many as a bullying and intrusive neighbor. U.S. government agents working in Mexico maintain a low profile to spare their government hosts any political fallout.
It's unclear how broad a net the new surveillance system will cast: Mexicans speak regularly by phone, for example, with millions of relatives living in the U.S. Those conversations appear to be fair game for both governments.
Legal experts say that prosecutors with access to Mexican wiretaps could use the information in U.S. courts. U.S. Supreme Court decisions have held that 4th Amendment protections against illegal wiretaps do not apply outside the United States, particularly if the surveillance is conducted by another country, Georgetown University law professor David Cole said.
Mexico's telecommunications monopoly, Telmex, controlled by Carlos Slim Helu, the world's second-wealthiest individual, has not received official notice of the new system, which will intercept its electronic signals, a spokeswoman said this week.
"Telmex is a firm that always complies with laws and rules set by the Mexican government," she said.
Calderon recently asked Mexico's Congress to amend the country's constitution and allow federal prosecutors free rein to conduct searches and secretly record conversations among people suspected of what the government defines as serious crimes.
His proposal would eliminate the current legal requirement that prosecutors gain approval from a judge before installing any wiretap, the vetting process that will for now govern use of the new system's intercepts. Calderon says the legal changes are needed to turn the tide in the battle against the drug gangs.
"The purpose is to create swift investigative measures against organized crime," Calderon wrote senators when introducing his proposed constitutional amendments in March. "At times, turning to judicial authorities hinders or makes investigations impossible."
But others argued that the proposed changes would undermine constitutional protections and open the door to the type of domestic spying that has plagued many Latin American countries. Colombian President Alvaro Uribe last week ousted a dozen generals, including the head of intelligence, after police were found to be wiretapping public figures, including members of his government.
