SUVA, Fiji — The methamphetamine drop-offs to a squatter settlement here followed a routine.

Once a week, according to residents, a black Dodge truck with tinted windows pulled up to a tent on the edge of the community, a dense maze of tiny shacks connected by muddy paths, slick from the persistent summer rain. A man stepped out, swapped drugs for cash with his local contact, and drove off. Dealers repacked the white crystals into tiny zip-top bags, no bigger than a child’s pinkie, before doling them out for about $22 each.