The San Luis Potosi state legislature approved the energy industry overhaul early Monday with the votes of lawmakers from the Institutional Revolutionary Party (PRI) and the Green Party.

Lawmakers from the leftist National Regeneration Movement (Morena), which was founded by former presidential candidate and Mexico City Mayor Andres Manuel Lopez Obrador, protested the vote by the San Luis Potosi state legislature.

A majority of Mexico’s 32 states had to approve the reforms, which are aimed at boosting sagging oil output, since they modify three articles of the Mexican Constitution.

The legislatures of Baja California Sur, Campeche, Chiapas, Coahuila, Durango, Mexico state, Hidalgo, Jalisco, Nayarit, Queretaro, Quintana Roo, Sonora, Veracruz, Yucatan, Tamaulipas and Puebla have also approved the energy industry overhaul.

Approval by the states was considered a given since the PRI governs 20 of Mexico’s 32 states and has large majorities in the state legislatures.

The Permanent Commission of Congress, which acts when the legislative branch is in recess, is expected to declare the initiative constitutional in the next few days.

The overhaul ends the 75-year monopoly over the energy industry enjoyed by state-owned oil company Petroleos Mexicanos (Pemex), opening the way for private investment in petroleum exploration and production.

Mexico’s lower house of Congress passed the energy overhaul bill last Wednesday.

The Chamber of Deputies approved the bill in general terms by a vote of 354-134 about 24 hours after the Senate gave the green light to the legislation.

The governing PRI and the conservative National Action Party (PAN) backed the measure to end a state monopoly over the industry that dates back to 1938.

The leftist Party of the Democratic Revolution (PRD) and its allies vehemently oppose the energy industry overhaul.

Pemex’s production has fallen by about 25 percent from a high of 3.3 million barrels per day in 2004 due to a sharp decline in production at Cantarell, formerly Mexico’s most productive field, and a lack of investment.