Mexico’s Congress on Friday approved a law backed by President López Obrador to extend the term of the head of the Supreme Court, despite controversy over the move’s constitutionality.

Chief Justice Arturo Zaldívar had admitted he was caught by surprise when the measure was added to a judicial reform bill at the last minute last week. He said in a statement it would be up to the Supreme Court itself to resolve any legal challenges to the law, which was passed last week in the Senate and on Friday in the lower house after hours of debate and objections raised by politicians from across the political divide.

He has ruled such moves unconstitutional in similar cases, including an attempt to prolong the term of a governor from the ruling Morena party in the state of Baja California.

Asked if he would stay on if the court ruled the extension constitutional, Zaldívar told Radio Fórmula “we would talk again then.” Meanwhile, “I am serving as chief justice of the court for the period for which I was elected.”

A two-year extension would mean Zaldívar’s term ends in 2024, when López Obrador’s presidency ends.

Critics have warned the move could set a precedent for López Obrador to seek to prolong his own mandate or install a justice over whom he could exercise control after he leaves office.

The president — who has weakened or attacked other key institutions including the electoral authority, INE, and pushed through energy reforms despite the Supreme Court ruling that key elements are unconstitutional — has dismissed such suggestions.

He said he believes the term extension is constitutional and without Zaldívar, an “honourable and principled” man, at the helm, judicial reform would be “dead in the water.”

However, Diego Valadés, a constitutional expert, said the timing was crucial, coming ahead of June 6 midterm elections in which López Obrador’s party is expected to trounce rivals.

“That would mean that most people would be legitimizing with their vote everything López Obrador has done against INE and in violation of the constitution,” he said.

Under Mexican law, presidents can only serve a single term. López Obrador has repeatedly said he would not seek re-election.

However, Porfirio Muñoz Ledo, a veteran politician and senior member of López Obrador’s Morena party, warned in response to the extension of Zaldívar’s mandate: “We’re coming to a crossroads in history. There’s no turning back. Either we go to democracy or we go to authoritarianism.”

José Miguel Vivanco, executive director of the Americas division at advocacy group Human Rights Watch, called the Zaldívar move “an unconstitutional reform which openly contradicts article 97, paragraph 4 of the constitution. It’s clear that Morena does not believe in the rule of law.”

That article states that the head of the court “cannot immediately be re-elected for a successive term” once his or her four-year term concludes.

© 2021 The Financial Times Ltd. All rights reserved. Please do not copy and paste FT articles and redistribute by email or post to the web.