Top gang leaders being sent back to El Salvador were part of a lengthy federal investigation that has amassed evidence of a corrupt pact between the Bukele government and MS-13.
Mr. Bukele, the Salvadoran president, agreed to help the White House carry out one of Mr. Trump’s signature policy agendas — the mass deportation of immigrants — by allowing scores of them to be housed inside his prisons where they would likely be beyond the reach of the U.S. justice system in exchange for millions of dollars and a request for the return of about a dozen senior members of MS-13 who were facing American charges.