Mexico's foreign secretary said Monday the country may take a dispute over U.S. plans to build a fence on the Mexican border to the United Nations. Luis Ernesto Derbez told reporters in Paris, his first stop on a European tour, that a legal investigation was under way to determine whether Mexico has a case. The Mexican government last week sent a diplomatic note to Washington criticizing the plan for 700 miles of new fencing along the border. President-elect Felipe Calderon also denounced the plan, but said it was a bilateral issue that should not be put before the international community....