Say they tested someone and a FALSE positive came up. UPS fires this person and then the e,employee gets a lawyer, sues for wrongful termination, they come back months later with full back pay and UPS has to pay there lawyers too lawyer and UPS probably ends up paying a "non-disclosed" amount as well. So lets say 1% of drug tests come back as false positives. With UPS's massive work force, that is millions of dollars down the drain trying to fire people for false positives. That is why there are multiple pages in the teamster contract about drug testing. If they could drug test on a whim, it would be used to harass everyone constantly. Same reasoning behind no lie detector tests. False positives happen