Hi there. It is illegal under federal law for an employer to discriminate against an employee or an applicant if the employer has 15 or more employees. The employer is also required to make reasonable accommodations for an employee with a disability.

If he feels like an employer did not hire him due to his disability he can file an EEOC complaint for discrimination. A good hiring manager (from a larger company) will know the law and it would probably be fine to mention it in the interview. In fact a lot of companies ask about this in their online application process, not to weed out, but to have all the information in case they happen to have to turn down an employee for an entirely different reason and that applicant files a discrimination complaint.

Either way, his employer will have to know eventually, so it's probably better to mention it at the end of an interview if he feels like the rest of the interview went well. For a smaller company, maybe try to down talk it a little, like "It doesn't happen often but I just want to let you know..."

See Americans with Disabilities Act of 1990 for more info.