Mexican President Andrés Manuel López Obrador makes no secret of his longing for the days when the state-owned oil monopoly, Petróleos Mexicanos, was a symbol of Mexican sovereignty. He seems to believe that with the right central planning, Pemex can return to the heady 1970s. To that end, he’s doing what he can to close the Mexican energy market.

Witness a side letter on energy signed by Washington and Ottawa as part of the new U.S.-Mexico-Canada Agreement. In it the two parties recognize the importance of “the integration...