Mexico’s states swiftly moved to remake the country’s entire judicial system on Thursday, approving an amendment to the Constitution that would be the most far-reaching judicial overhaul ever attempted by a large democracy.

The measure, which would replace the current, appointment-based system with one in which voters elect judges, would put Mexico onto an untested course whose consequences for the courts and the country are nearly impossible to predict.

Proponents of the plan argue it would reduce corruption and give voters a greater role in a justice system widely regarded as broken. Critics of the overhaul accuse the Mexican government, which proposed and pushed for the changes, of endangering the rule of law by politicizing the courts, giving Mexico’s ruling party greater control over judges and eroding the country’s checks and balances.

The overhaul could see thousands of judges removed from their jobs, from those in local courtrooms to the chief justice of the Supreme Court. And it would drastically restructure a major branch of government responsible for meting out justice across the third-most populous country in the Americas.

The logistics alone are daunting: The country would need to implement new elections for thousands of judges, starting next year.

Mexico’s Senate passed the amendment on Wednesday. And by Thursday morning, a majority of state legislatures had approved the amendment, ensuring that it would reach the desk of the outgoing president, Andrés Manuel López Obrador. He has long championed the measure, which has for weeks brought thousands of people into the streets, both in opposition and support, and drawn warnings from the U.S. and Canadian ambassadors and legal experts.