Opium is nestled between the U.S. and Atzlan. It is a country itself, run by El Patron. The entire use of the land, it so that opium can be grown and be sold as drugs to all parts of the globe. The U.S made a deal with El Patron: if he can put an end to illegal immigration coming from Atzlan to the U.S, his empire would be legal.
In order to combat the immigration and keep his empire afloat, El Patron created the Farm Patrol; a fleet of mercenaries (under his control) that capture any fleeing illegals coming from Atzlan. The people who are caught will be turned into eejits.
As mentioned in the book frequently, an eejit is a person that's turned into mindless zombie with a computer chip in their brain that commands their every move. A majority of the eejits are immigrants who tried to flee from Atzlan, but also consist of maids, enemies, random people, etc. who El Patron deemed useless. They do simple things, but most of them work long hours in the fields, tending the opium all year round without any hesitation.