Can you just be fired for using a drug that you took long before starting a new job?

Question Details: wasn't looking for a new job but a headhunter presented me an opportunity that I couldn't resist so I was flown from OH to TN for the interview. The following week they presented a very attractive offer and I accepted. I resigned from my job at that time, turned in notice on my apartment, packed everything up and made arrangements to have it moved down and have utilities shut off. Last Wednesday they had me go to a place in OH that collects their hair follicle pre-employment drug test I drove myself down here on Sunday and started work the next day, life was great. Then, just after lunch, I was told that my drug test came back positive and to call the medical examiner. She asked me if I've ever done methamphetamine. I wasn't going to lie and said I have in the past but not anytime recently. She said that she had to turn in a positive result because sometime in the last year I used this drug. I was then terminated. This can't be legal. I haven't done anything wrong and in a split second my life has been turned completely upside down. What am I supposed to tell my family and friends that don't know anything about drugs and me, which is how I like it. I hardly ever do hard drugs. I don't even know what to do. I've paid everything out of pocket relying on the relocation money I'm supposed to get tomorrow. I don't even have money to get home. I offered to go in and take a urine test but I wasn't given any suggestions or options, just that I needed to leave.

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