No. But an employer may choose to conduct preemployment alcohol tests (unless under US Coast Guard or RSPA rules) under DOT authority if the following conditions are met: Testing is accomplished for all applicants, the testing must occur after the employee has been told s/he has the job if the test is passed, and the testing must comply with DOT regulations in 49 CFR Part 40.
Information about the reasons for which employers perform alcohol tests on their employees is contained in the regulations for the specific operating agency that governs the employer.