Failure of a non-federal drug test is not the same as failing a federal drug test. It also does not constitute Actual Knowledge.
But a positive non-DOT drug test does make the driver medically unqualified to perform safety sensitive duties. Under 49 CFR Part 391.41(b)(12), the driver is to be removed from driving duties and is medically unqualified for the duration of the prohibited drug use.
Before he or she can resume performing safety-sensitive work (i.e. drive), the driver must be examined by a Certified Medical Examiner, who may determine that the driver needs to see a Substance Abuse Professional (SAP), complete a drug rehab program and/or have a negative drug test result.
Once the medical examiner has determined that the driver is drug free, the driver may return to safety-sensitive duties. Since this is a non-Federal drug test, the requirements of 49 CFR Parts 382 and 40 and the Return To Duty process do not apply.