MEXICO CITY—A majority of Mexican state legislatures have approved changes in the constitution that open the country's state-run energy industry to greater private investment and end a 75-year-old monopoly of state oil company Petróleos Mexicanos.
     Early Monday, San Luis Potosí became the 17th state to vote in favor of the bill, which amends the constitution to allow for private firms to explore for and produce oil and gas for the first time since the 1938 expropriation of the industry.
     Constitutional amendments in Mexico require a two-thirds majority vote in the Senate and lower house, and approval by a majority of the 31 state legislatures.
      Last week, the Senate and the lower house of Congress approved the changes, which amend the three constitutional articles that formed the core of the country's restrictive energy laws. With the necessary state approvals, the Congress can declare the changes constitutional and send the bill to President Enrique Peña Nieto to be signed into law.
      Mr. Peña Nieto, who is on a state visit to Turkey, said he would sign the bill as soon as he gets it back from Congress, which he expects in the coming days, according to a transcript from the presidential press office.
      Once that happens, the government and Congress have four months to draw up the enabling legislation that will include, among other things, details of the contracts that will be offered.
Under the new energy laws, private oil companies will be allowed to produce oil and gas, either sharing profits in joint ventures with the government, sharing production, or under licenses where they will pay royalties on oil produced.
      It also opens up oil refining, electricity and other areas of the energy industry to private concerns.
     Passage of the energy bill, which was supported by the ruling party and conservative opposition but opposed by leftist opposition groups, marks the high point in a number of legal changes that Mr. Peña Nieto's administration managed to pass in its first year to raise the country's long-term growth potential. Earlier overhauls were made in education, telecommunications, banking and tax laws.
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