Is spending Social Security disability benefits on illegal drugs fraud?

I know a mother/son team who both draw social security disability. They spend the majority of it on marijuana (living in a state that does not recognize medical marijuana in any way shape or form). Recently they have begun using disability money to buy large quantities and sell. My question is, is this purely a matter for law enforcement? Would social security care? What could they do besides drug test them? They also take the Lortabs paid for by medicare, and trade them for marijuana or sell them to family and friends for cigarette money. It just galls me that I have to get up and go to work every day and they get to sit home and smoke dope all day and scratch their es on the taxpayer's dime. Thanks for any input.