A PhD student I know was terminated because of mental illness without any accommodation. What is the possibility of legal action? This question is related to the experience of a close relative. He was a PhD student in the US. During his PhD, a little over a year ago, he was hospitalized with his first episode of mental illness. His advisor immediately terminated his employment telling me that my relative was not fit to do a PhD in his lab. He further told me that he had worked with a mentally ill student in the past and it was a mistake and he cannot repeat the same mistake with my relative. While it hurt to hear that, I didn’t think much about the termination at that time as my first priority was helping with the relative's treatment and getting him back on his feet. He had to leave the country since he could not be on a student visa without employment and he has been staying at home since. The drastic life change and not having an independent source of income have been stressing him out and he recently had his second episode. I know this is a complicated situation but am I crazy in thinking that the professor discriminated against my relative by not considering any reasonable accommodations before letting him go? My relative is not a US citizen and is living outside the US now but is there a legal course we can follow? This has been an excruciating experience for our family and any advice/tips are greatly appreciated.

Note: There were no warning signs of the illness before it manifested and my relative was in great standing with the advisor - his research was going well, he had good grades and was not a cause of concern in any manner.
As others have said, this is probably a question for a lawyer. That said, we don’t have any idea of what kind of information  the advisor/university/HR dept has. Perhaps they had information that made them think they had just cause. It could be that your relative is either ignoring or perhaps just overlooking something you don’t know. 

Depending on the environment, mental health issues could be a cause for termination because it would make you unfit or ineligible to continue. If the research involves very dangerous products (infectious organisms, highly lethal compounds) or a strict environment (BSL4, secure environment such as a government facility), the terms were probably spelled out somewhere in a document your relative signed.