I think it being allowed for employment is also bull **** but I also believe in the right of organizations to do as they see fit within reason. Drug testing is a superficial measure that only tests for marijuana with any kind of practical efficacy while it's arguably the least harmful drug ( when compared to substances of varying legality like alcohol, tobacco, opiates, and benzodiazipines). If a welfare recipient has a taste for just about any other drug - especially alcohol, coca, or amphetamines - then they can just use those within one day of a test and be fine so long as they aren't abjectly vegetative with their lifestyle and/or don't drink water.
It's all rather silly.