can i access their policies? And is this discrimination?

I was recently refused for rehire based on a failed urinalysis. An employee who was charged and convicted of DUI, violated his probation and went to jail for 30 days was immediately rehired upon his release from jail. I believe I am being discrimated against although I do not fall into "the protected class." immediately following my drug test, I informed the director of operations that I may fail. I asked if I should inform HR or my manger and he said no. Based on the small amount of marijuana I had smoked, he told me to wait it out because I might pass. I did not and was fired. the incident involving the guy who was arrested happened before this. Its been a year since I was fired and i just attempted to re-apply after the director of operations told me to, he is a friend. I feel like either their policies are discriminatory or someone there is telling HR not to rehire me. I asked for proof of their policy on rehires and my request was rejected.