WASHINGTON—No one who has talked to Colombian President Alvaro Uribe can be surprised that his country’s Senate has now approved a constitutional referendum that would allow him to run in 2010. Uribe thinks that the presidency remains his destiny.

There are still some institutional obstacles, particularly the Constitutional Court, but the decision will almost certainly be made by Colombians at the polls. The law requires a turnout of at least 25 percent—almost the same number of people who voted for him when he was re-elected in 2006. For the good of Colombia, Uribe, the most successful Latin American president in a generation, must be stopped.

There is no excuse for running again. There are many candidates, including his former defense minister, Juan Manuel Santos, who are perfectly capable of continuing Uribe’s policies based on fighting Marxist terrorists and fostering a business climate conducive to investment. The argument Uribe made the last time he changed the constitution—that progress could be reversed because the enemy was still powerful—is no longer valid. The terms of the Colombian conflict have been inverted: It is now the Revolutionary Armed Forces of Colombia (FARC), not the state and civil society, that is on the run. The economy, strained by the global recession, is in much better shape than it was. Anyone seeking the presidency will be forced by a critical mass of Colombians to embrace “democratic security” as well as private investment and open trade.

But ultimately the reason why Uribe should be stopped has little to do with utilitarian considerations. The rule of law, a fundamental principle of civilization, is at stake. What Uribe is trying to do is what most Latin American rulers have historically done and what the region’s populists continue to do. His nemesis, Venezuela’s Hugo Chavez, can run indefinitely. Bolivia’s Evo Morales and Ecuador’s Rafael Correa have changed their constitutions for their own benefit; Nicaragua’s Daniel Ortega and Honduras’ Manuel Zelaya are attempting the same.

No one has ever accused these leaders of standing for the rule of law. But Uribe made the rule of law the linchpin of his presidency. Many of the ugly truths in Colombian society—the umbilical cord linking the paramilitary groups to the establishment, the abuses committed by the armed forces, the widespread corruption originated in drug money—have come to the surface because of policies that facilitated the involvement of judicial institutions in what used to be beyond the reach of the law and because, unlike Chavez, Uribe has not sent journalists into exile or expropriated media outlets. By periodically subjecting the constitution to the vain whims of the president, Uribe is undoing everything he has done for his country.

Latin America’s problem was never economic; it has always been political. The failure to achieve prosperity is a byproduct of the weakness of institutions that failed to limit power and protect people’s freedoms and possessions. At the end of the 1940s, Mariano Ospina Perez, one of Uribe’s predecessors, unleashed a civil war that took the lives of 200,000 people precisely because he thought himself bigger than the constitution. In Mexico, the reign of Porfirio Diaz, justified by intellectuals of the French-inspired “positivist” school that thought dictatorship would accelerate progress, led to the Mexican Revolution—a carnage that took a million lives. The “positivist” Brazilians who ruled the country after the fall of the monarchy in the late 19th century turned the military into the dominant institution—and eventually opened the doors of power for Getulio Vargas, a man influenced by fascism.

These leaders, and many others, had one thing in common—an inability to understand that progress does not come from twisting the law to fit one’s social blueprint or megalomania, however admirable that blueprint and however justified that person’s high concept of himself.

Uribe’s supporters think his triumph has been the near defeat of Marxist leftists in Colombia. His real triumph has been the progress made by the rule of law in many areas; the near defeat of the Marxists was the consequence of that progress. If he goes ahead with the referendum and wins, the rule of law will have suffered and his Marxist foes will have snatched victory from the jaws of defeat.