Mexico's energy regulator punished Spanish corporation Iberdrola for $467 million for inappropriately selling electricity to third parties in breach of local "self-supply" legislation, according to a document published Friday, 

The Energy Regulatory Commission (CRE) stated that Iberdrola "was required to generate power exclusively to satisfy the self-sufficiency needs of its partners... and not to sell, resell, or dispose of capacity or electricity by any legal action," according to the document.

Private electricity generators in Mexico are required by contract to only supply energy to the specified partners listed at the time the contract is signed.

Surpluses from private generators may be sold to the state-owned Federal Power Commission (CFE), which has a monopoly on electricity transmission and distribution to end-users.

The infractions happened at Ibedrola's branch in Monterrey's northern industrial district between January 1, 2019, and August 31, 2020, according to the CRE document.

The fine comes at a difficult time for Mexico's electricity industry, as President Andres Manuel Lopez Obrador attempts to re-nationalize it.

In April, Mexico's Congress rejected a constitutional reform package that would have extended the role of the state in power generating, a key priority of Mexico's left-wing government that the US has publicly condemned.

That reform would have overturned a 2013 decision to privatize Mexico's energy sector and given the state-owned Federal Electricity Commission (CFE) more influence over the private sector and international corporations.