46 CFR §16.210

1. (a)No marine employer may engage or employ any individual to serve as a crewmember unless the individual passes a chemical test for dangerous drugs for that employer.
2. (b)An employer may waive a pre-employment test required for a job applicant by paragraph (a) of this section if the individual provides satisfactory evidence that they have:
   1. (1)Passed a chemical test for dangerous drugs, required by this part, within the previous six months with no subsequent positive drug tests during the remainder of the six-month period; or
   2. (2)During the previous 185 days been subject to a random testing program required by § 16.230 for at least 60 days and did not fail or refuse to participate in a chemical test for dangerous drugs required by this part.