Mexico’s Supreme Court deemed constitutional Thursday a controversial energy law pushed by President Andrés Manuel López Obrador that gives government-owned power plants preference over private competitors.

The law took effect in March 2021, but a number of private energy companies sought injunctions blocking enforcement. With the law ruled constitutional, the injunctions will now have to be resolved.

The law establishes that electricity must be bought first from government power plants, which use primarily coal, oil and diesel to produce energy. If demand requires it, additional electricity could be purchased from private wind, solar and natural gas plants.

Jesús Ramírez, presidential spokesman, celebrated the court’s decision. “History will judge those who betray the country and the interests of Mexican people,” he said via Twitter.

Critics, including the United States government, maintain the law will undermine competition in the sector, hurt the environment and violate free trade agreements.

He said the U.S. hopes “the legal framework that emerges will support the creation of a North American clean energy powerhouse, protect current and future U.S. business investments in Mexico in accordance with Mexico’s obligations under the United States-Mexico-Canada Agreement, and protect the integration of U.S.-Mexico supply chains for the prosperity of our region.”

The justices reviewed the law piece by piece and repeatedly returned divided votes that were not enough to overturn it. The constitutional challenge had been brought by the law’s opponents in the Mexican Senate. The court’s formal written decision will not be published for weeks.