From the Document: "Criminal activity along the Southwest Border (SWB) poses a significant national security threat for the United States. The almost 2,000-mile border that separates the United States and Mexico includes major population centers, transportation hubs, and large tracts of uninhabited desert. Criminal organizations have used that vast area to engage in cross-border drug trafficking, human smuggling, weapons trafficking, money laundering, and other associated illegal activities. The U.S.-Mexico border is the primary entry point into the United States for all major illicit drugs, with the exception of controlled prescription drugs and certain new synthetic drugs. Mexican Transnational Criminal Organizations (TCOs) operating primarily on the Mexican side of the U.S.-Mexico border supply the majority of the heroin, methamphetamine, cocaine, and foreign-produced marijuana available in U.S. illicit drug markets. These drugs are also smuggled into the United States across other land, sea, and air frontiers, but not on the same scale as the substances transported across the SWB."
The White House: https://www.whitehouse.gov/