Mexican President Andrés Manuel López Obrador’s government claimed inefficiencies in supply chains were behind a recent and temporary nationalization of private assets.

AMLO

Last Friday, the military seized part of a rail line owned by Grupo Mexico SAB unit Ferromex in the southern state of Veracruz. The railway is part of the Interoceanic Corridor project crossing the 77-mile Isthmus of Tehuantepec, the narrowest strip of land in Mexico between the two coasts. It is also one of the president’s flagship projects.

López Obrador justified the grab on the grounds that the project was of national security and public interest. The government said the rail owners would be compensated.

Albeit temporary, this would be the first instance of an outright expropriation under López...