Mexico's Pride, Its Oil, May Reopen to Big Multinationals Dario Lopez-Mills/Associated Press Oil workers lowered a drill off the coast of Veracruz in the Gulf of Mexico in November. CIUDAD DEL CARMEN, Mexico - Every gas station in Mexico is stamped with the green-and-white logo of the state-owned oil monopoly, the economic lifeblood of the government. Oil Expropriation Day, commemorating the day Mexico seized control of the industry from multinationals in 1938, is celebrated with speeches and even parades in some towns. An old song, "The Oil Worker Hymn," credits oil with "saving our fatherland." But now, President Enrique Peña Nieto, in what could be the biggest economic change in two decades, is on the verge of rewriting the constitution to open Mexico's oil, gas and electricity industry to private investment - a provocative move that could shake up the North American energy industry and test the storied grip Mexico's oil has had on its soul. "We must defend our oil," Cuauhtémoc Cárdenas, the three-time presidential candidate and son of the revered president who nationalized the oil industry, declared in a recent television advertisement. The state oil company, he said, "is a business belonging to all Mexicans and we must not allow it to go private." The legislation, which won final congressional approval on Thursday afternoon, declares that Mexico still owns its oil. But it allows private companies to drill for oil and natural gas in partnership with the state monopoly, called Pemex, or on their own, returning international oil companies to territory they were kicked out of 75 years ago. In a country where controlling oil is often equated with sovereignty and national pride, the plan has set off furious debate. But while demonstrations helped thwart a more tepid attempt to open up the industry in 2008, they were not effective this time - though there were some colorful moments. As the lower chamber raced to give preliminary approval in the early hours of Thursday, one leftist lawmaker opposed to it stripped down to his black underwear to symbolically suggest that the country was giving away its most treasured resources. The change must now be ratified by just over half of Mexico's states before it becomes law, but Mr. Peña Nieto's party controls a majority of them. The stated goal is to stimulate Mexico's sliding oil production and vault the country into the developed world by tapping vast pockets of oil and natural gas deep under the earth and sea. Foreign oil companies have long been eager to gain access to Mexico's oil and have quietly lobbied the government to open up for years, while Pemex is known for inefficiency at best, and corruption at worst. "They know Mexico; they have been waiting for a long time for a true opportunity," Jeremy M. Martin, director of the energy program at the Institute of the Americas, said of international oil companies. The energy overhaul is the centerpiece of a series of changes Mr. Peña Nieto has pushed through this year with mixed results, including an effort to break up telecommunication monopolies, raise taxes and weaken the teachers union grip on faltering public schools. His Institutional Revolutionary Party - which nationalized the industry in the first place, setting Mexico on its course toward industrialization - joined with conservative lawmakers who have long wanted the energy changes, casting off a politically weakened left. Opinion polls suggest Mexicans are growing impatient with Mr. Peña Nieto's agenda and do not yet feel any benefits from it, as economic growth has slowed and the violence he promised to tackle persists largely unchecked. But he is banking that a change in energy policies will inject new life into the economy. Other presidents have failed in taking on the oil monopoly, a lifeblood to government coffers and a touchstone for the left. "Oil has symbolic power in Mexico that it does not have in every oil country," said Noel Maurer, a Harvard Business School political economist who has studied the industry. "Mexico has built up national mythologies that "the oil is ours." It's like a flag-burning issue. Randal C. Archibold reported from Ciudad del Carmen and mexico city, and Elisabeth Malkin from Mexico City. Clifford Krauss contibuted reporting from Houston.