U.S. politicians and much of the news media understandably have been preoccupied with the recent nerve-wracking developments involving North Korea. However, there are important security developments taking place at the same time next door in Mexico. U.S. officials need to open their eyes.

There are both encouraging and worrisome signs regarding the power of Mexico’s drug cartels. Killings are down, but vigilantism is rising.

The country’s new president, Enrique Peña Nieto, who took office in December, has adopted a more restrained tone regarding the drug war. Gone is the confrontational, bombastic rhetoric of his predecessor, Felipe Calderón, about inflicting a crushing military defeat on the traffickers. Instead, Peña Nieto has sought to dampen tensions, emphasizing the need to restore peace to the country. And there have been some positive signs.

The pace of killings in cities on the border with the United States, especially Ciudad Juárez, long the epicenter of the carnage, has declined in recent months. Although the principal reason for the decline in Juárez apparently is the Sinaloa cartel’s decisive victory over its rivals, beleaguered residents welcome the emergence of greater calm, whatever the underlying cause.

But there is another development in various areas of Mexico that poses bad news for both the cartels and the Mexican government: the sudden surge in vigilante groups. It is not entirely a new phenomenon. As far back as 2009, there were sporadic reports of such groups taking action against drug gangs and other criminal elements. The origins and motives of the vigilantes were murky from the outset. Some appeared to be little more than fronts for rival traffickers, but others seemed to consist of ordinary citizens who were fed up with all the violence and the apparent inability of the Mexican government to stop it.

What has changed in recent months is the number of episodes involving these so-called self-defense organizations. In January 2013, the Associated Press published a lengthy report on the rise of such groups, especially in the western states of Guerrero and Michoacan. Although members were armed mostly with aged weapons, they proceeded to establish checkpoints on local roads. They also arrested more than 40 people on various charges and held them in makeshift jails. “In less than a month, they have done something that the army and state and federal police haven’t been able to do in years,” one Guerrero resident told the AP.

But the rise of the vigilantes also has negative implications. In late March, vigilantes took control of Tierra Colorada, a small town on the main highway connecting Mexico City and Acapulco, the resort city ravaged by drug-related violence in recent years. The self-defense council not only established improvised checkpoints on that highway—they arrested 12 members of the local police force as well as the former director of public security.

Although the Mexican people, weary of the government’s inept campaign against the drug cartels, might understandably be tempted to cheer-on the vigilantes, the growth of such groups is not, on balance, a healthy development. By definition, vigilantes do not operate according to robust standards of due process. The danger of innocent individuals being detained—either through error or the result of personal vendettas—is a major worry. So, too, is the risk of hapless parties being attacked by ill-trained, undisciplined gunmen. In two separate incidents in early 2013, tourists driving through the Tierra Colorada area were wounded when they failed to stop for a vigilante checkpoint.

Beyond the potential for injustice and tragic mistakes, a surge in vigilantism is inherently a worrisome sign of a dysfunctional political system. Indeed, it is sometimes an early indicator of the potential for a country becoming a “failed state.” What seems to be occurring in Mexico today is reminiscent of developments in Colombia during the peak of that country’s political turmoil and drug-related carnage from the early 1980s to about 2006.

The apparent new popularity of self-defense councils suggests that some Mexican citizens have completely lost confidence in the government and have decided to fight back on their own against the cartels and the damage they are inflicting on the country. That is what happened in Colombia when conservative factions formed right-wing paramilitary organizations (as well as outright death squads) to attack the Revolutionary Armed Forces of Colombia (FARC) and other radical left-wing insurgent groups—and selected trafficking organizations. The Colombian vigilantes sparked an additional surge in violence that convulsed the country and intensified an already simmering civil war. It took a monumental effort by the administration of President Álvaro Uribe to both weaken the FARC and disarm the paramilitary militias.

A significant vigilante movement in Mexico would certainly not enhance that country’s stability. Given Mexico’s political, economic, and strategic importance to the United States, the Obama administration needs to watch this latest development with at least as much intensity as it is devoting to North Korea.

Ted Galen Carpenter, a senior fellow at the Cato Institute and a contributing editor to The National Interest, is the author of nine books, including The Fire Next Door: Mexico’s Drug Violence and the Danger to America.