The meeting in Richmond, Va., quickly dispensed with routine matters, including introductions, before the senior leadership got down to business. Teamwork and recruitment, said one top official, needed improvement. Also, anyone wanting to kill a rival must secure prior approval.

Mara Salvatrucha, the violent international street gang known as MS-13, had its share of headaches by the time of its fall 2015 meeting, which was surreptitiously recorded by U.S. authorities. One proposed solution was to better manage its estimated...