If you have such a policy or are considering one, make sure to consult an employment attorney. The laws in this area change so frequently, it’s difficult to know what is acceptable and what isn’t.
For example, a candidate for a part-time page at a city library in Oregon was required to take a drug test. She refused and sued. The Ninth Circuit Court of Appeal upheld, deciding this was a violation of the 4th Amendment. (Lanier v. City of Woodside)
In California, pre-employment testing is – in many cases – acceptable. But ask yourself what would require the need for drug testing? If it’s a receptionist, what is the rationale? It’s more understandable if the position requires an employee to drive, or handle cash, or operate machinery. Make sure your decision to drug test is correct for the position and your company, and always consult counsel before implementing such a plan.