sentences:  Boundary disputes and allocation of boundary waters have been administered since 1889 by the International Boundary and Water Commission, which also maintains international dams and wastewater sanitation facilities.Once viewed as a model of international cooperation, in recent decades the IBWC has been heavily criticized as an institutional anachronism, by-passed by modern social, environmental and political issues.Illegal immigration, arms sales, and drug smuggling continue to be contending issues in 21st-century U.S.-Mexico relations.