The revised NAFTA deal will likely have a stand-alone energy chapter. That’s been an important aim for the Mexican government, which wants to lock-in its 2013 energy reforms ahead of national elections in July that it may lose. Such a chapter would also be in America’s interest, on the basis of the Trump administration’s focus on the trade deficit.

Mexico imported $19 billion more energy (including coal, oil and gas) from the U.S. than it exported in the 12 months to January 31. That represents a $29 billion “swing” from the surplus Mexico ran in 2013. A mixture of energy reform a...