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The justices said López Obrador’s Morena party changed the electoral legislation after it was approved in Congress.

The reforms would have reduced the spending and size of the country's independent National Electoral Institute, and limit its authority to oversee political parties and candidates.

López Obrador has accused the high court of overstepping its authority by judging whether Congress followed its own rules.

In May, the court overturned another part of the electoral changes because Congress rushed the measure through to a vote without debate, or even time to read it.

López Obrador has a habit of demanding legislators approve bills they often receive just a few hours or even minutes before, often late at night or in the early morning hours.

Mexico's constitution requires congress to consider and debate any laws it passes. In one case, justices ruled that changes were made to the text of one of the bills without telling the legislators before they voted on it.

The laws struck down in May involved electoral rules limiting partisan activity by politicians who hold public offices. López Obrador had sought to loosen limits on what public servants can say about electoral races or how they can use government advertising.

The president’s office has accused the Supreme Court of violating the separation of powers by overriding the legislative branch. The justices say the legislative branch has to follow its own rules.