yes.
a company must inform you of their plans to test for drugs. they must tell you how it's going to be done, and they must tell you the concequences of testing positive.
there's some places where a positive test cannot mean immediate termination by law. if they test for drugs, they must offer a form of rehab as an alternative to termination.
not only that, if a company says they perform random drug tests, they must show the process of randomization they use. they can't just say they're giving random drug test and randomly only test the pot-head looking employees....