How do people get marijuana in states where it's not legal?

"Despite continuing increases in the amount of cannabis produced domestically, much of the marijuana available within the United States is foreign-produced. The two primary foreign source areas for marijuana distributed within the United States are Canada and Mexico. Mexican drug trafficking organizations (DTOs) have relocated many of their outdoor cannabis cultivation operations in Mexico from traditional growing areas to more remote locations in central and northern Mexico, primarily to reduce the risk of eradication and gain easier access to U.S. drug markets. Asian criminal groups are the primary producers of high-potency marijuana in Canada."

Source: 

National Drug Intelligence Center, "Domestic Cannabis Cultivation Assessment 2009," (Johnstown, PA: July, 2009), p. 1.

Subject: 
Substance: