Since the 1970s, U.S. agencies have recognized that high-volume cigarette sales at duty-free stores near the U.S.–Mexico land border, although lawful, could be related to illicit activity. In 1988, U.S. law limited the quantity of duty-free tobacco products an individual can purchase at stores located in airports, restricting the sale of tobacco products to quantities consistent with personal use. This requirement, however, does not apply to land border duty-free stores...