I am not much on legal matters. I can tell you that EtG testing is a medical examination
and not a drug test
as those terms are defined in EEOC and ADA* rules and regs. The fact that you are seeing a psychiatrist, depending on diagnosis, may grant protections under the latter.
If you feel it necessary to obtain a lawyer you should look for one in employment (labor) law that understands the ins-and-outs of the ADA and employee exams and tests.
Someone is grossly misinformed about the uses and appropriateness of testing methods.
*Equal Employment Opportunity Commission guidance
Americans with Disabilities Act