My husband worked for Davey Tree in Jefferson City TN for a few months and after coming back from hurricane damage work he was fired

It took my husband 2 months and 2 drug screens and 2 applications to get a job at Davey tree in Jefferson City TN. He went to Ga. and FL. for about 3 weeks and right after he came back his supervisor told him the HR from the main office called and told him since my husband had a drug charge on his background to watch him and if he appeared high or messed up to fire him and the supervisor told my husband what was said and he told my husband he had nothing to worry about and then the following day after no write ups my husband was fired and he received a adverse action letter in the mail so he called the number on the letter and and asked them why he was fired and they told him they couldn't hire him because of his background and he tried to explain to them he had been working for them almost 3 months. Is this legal or wrongful termination? Plz help.