A former official fires a legal missile at Mexico’s political class

ONE OF THE rituals of Mexican politics is for a president to begin his term by locking up a supposed miscreant from the previous administration. Four of the six presidents from 1982 to 2018 did that. They incarcerated two union leaders, a former president’s brother and the head of Pemex, the state oil company. They presented these as giant victories in the fight against corruption. But they were not. Two of the jailbirds were acquitted, one was pardoned and the sentence of the fourth was overturned. Corruption continued to be rampant, uninvestigated and unpunished.

Many Mexicans regard the administration of Enrique Peña Nieto, which governed until December 2018, as the most corrupt in history. Rosario Robles, a minister in his government, is suspected of helping to siphon off $400m of the government’s money through ghost companies and has spent the past year in preventive detention. A construction firm with government contracts helped Mr Peña’s wife acquire a house worth $7m.

Those scandals helped Andrés Manuel López Obrador, a left-wing populist, win the presidential election in 2018 in a landslide. Mr López Obrador, often called AMLO, portrays himself as incorruptible and promises to “eliminate, not reduce” graft. Like past presidents, he has sought out wrongdoers from earlier administrations.

Last year, at the...