Last week, revisions to Mexican federal law took effect that give public authorities and law enforcement unprecedented ability to compel mobile phone companies to disclose real-time geographic data from mobile phone companies in a wide variety of cases.

The group of legal revisions, popularly known collectively online as the #LeyGeolocalización (Geolocalization Law), appears to be squarely aimed at expanding police power to fight drug violence and gangs in a massive conflict primarily fought along the United States-Mexico border for decades. As new data found from the ACLU and EFF shows, local law enforcement across the United States are likely routinely using a similar practice. The Mexican law codifies what local and federal government in the US have been doing in practice for years.

The bill passed the lower house of the Mexican parliament on March 1 by an overwhelming margin, 315 votes in favor, seven against, and six abstentions. The Mexican government and law enforcement have argued that they need more extensive surveillance power as a way to fight cartel-related violence and kidnappings.

Just before the bill passed, Alejandro Martí, the president of Mexico SOS, an advocacy group fighting against violence and kidnapping, reminded Mexican lawmakers that his group had initially proposed the law 10 months ago. Martí’s son was murdered on his way to school in 2008.

"Unfortunately, yesterday [February 28] marks 10 months that the bill has been sitting in the House of Representatives and has not been approved," he was quoted by the Mexican newspaper El Universal as saying in remarks before the National Security Council. "[During that time] there have been 2,252 kidnappings, 61 hostages killed, not taking into account the 3,474 cases of telephone extortion of kidnapped migrants."

Mexican activists, attorneys argue against reforms

Not surprisingly, Mexican attorneys and human rights activists are speaking out against these expanded powers, arguing that despite the law’s good intentions, it is far too over-reaching.

Most notably, Luis Fernando García Muñoz, a Mexican law student at the University of Lund (Sweden), has published a 23-page, Spanish-language legal analysis arguing against the constitutionality of the legal changes. He has also spearheaded a petition to Mexico’s Human Rights Commission. (So far, the petition has only received around 200 signatures.)

One of the main arguments against this expansion of police power is that local Mexican judicial officials and law enforcement cannot be trusted with such unchecked power, particularly when many states have been victim to corruption by drug cartels.

"The alternative to [challenging this law] is the belief that the Attorney General, the Solicitor General of Veracruz, Chihuahua, Durango or any other state (with a history of having been infiltrated by organized crime, it’s difficult to have faith in them) can monitor your cell phone and neither you, nor a judge, nor anyone can prevent the State (or organized crime) from abusing that power," Muñoz wrote last week in a Spanish-language blog post.

Others, including the Mexican chapter of Article 19, agreed.

"The main problem with this law is that it doesn’t contemplate any warrant from the government," Antonio Martinez, the spokesperson of the group told Ars on Tuesday. "It’s outside [normal] judicial power."

On the northern side of the United States border, Katitza Rodriguez, the international rights director at the EFF, called the Mexican legal reforms a "time bomb for abuse."

"The Mexican Government knows what it's getting," she wrote in an e-mail sent to Ars on Tuesday. "This is sensitive information that reveals so much information about where people go. In an environment where it is dangerous for bloggers to report sensitive information about drug-related violence—especially since this information is rarely reported in local newspapers or on television. It is important that [the Mexican Government] protect the privacy and location of Mexicans by requiring a warrant under reasonable grounds prior to requesting the monitoring of the online information."

American attorney says Mexicans will be at higher risk

On Tuesday, an American IT attorney and legal scholar living in Mexico hand-delivered a nine-page English-language legal analysis arguing against the legal revisions to the office of the Federal Police in the state of Morelos, outside of Mexico City.

In the letter, she argues that the new law revisions are harmful to Mexicans not only due to their potential abuse by narco-infiltration, but also because it weakens existing law that requires SIM card registration.

"Under prior law, cell phone purchasers were required to register user data as a prerequisite to purchase of a cell phone," wrote Lisa Brownlee.

"Commendably, this requirement has been eliminated by LeyGeolocalización MX, and the database is scheduled to be destroyed. Remarkably, however, IFAI [the Mexican data protection authority] itself does not even know the location of that database, and copies of it are readily available for purchase. This data, coupled with real-time geolocation data, will result in unprecedented enhancement of criminals' ability to target unsuspecting victims. For this reason too, the law will cause more harm than good. It makes extant potential victims—particularly high-value ones such as family members of wealthy citizens."