Mike

Tough call. Disability discrimination is always tough to prove as the employer usually claims that there was no "reasonable accomodation" that would let the employee perform the essential duties of the job which is a complete defense. Practically he needs to file a complaint with the state agency and EEOC.
Here's a good summary by EEOC of the legal rights
Q & A cancer
However, while this pamphlet sounds great, in real life the EEOC usually does not do anything which is why you have the right to demand a "right to sue letter" after they've sat on the case 180 days. However it is free to file a complaint and sometimes companies do settle when contacted. No attorney fees if your friend sticks with the EEOC. At this point, what does he have to lose?