There are several laws which protect the workplace rights of Americans with disabilities. Included are several sections of the Rehabilitation Act of 1973. These sections prohibit federal agencies from discriminating against qualified individuals with disabilities, require contractors and subcontractors who have a contract with the federal government for $10,000 or more annually to take affirmative action to employ and advance in employment qualified individuals with disabilities, prohibit recipients of federal financial assistance from discriminating against qualified individuals with disabilities in employment and in their programs and activities, and require that individuals with disabilities, who are members of the public seeking information or services from a federal department or agency, have access to and use of information and data that is comparable to that provided to the public who are not individuals with disabilities. Individual states may also have anti-discrimination laws on the books.
The law with which people are most familiar is the Americans With Disabilities Act of 1990 (ADA). Title I of the ADA covers employment. Since 1994, it has required that employers of more than 15 people must make reasonable accommodations that allow a qualified job applicant with a disability to complete the application process or a disabled employee to carry out the duties of his or her job. According to the Americans With Disabilities Act, "an individual is considered to have a disability if s/he has a physical or mental impairment that substantially limits one or more major life activities, has a record of such an impairment, or is regarded as having such an impairment."
It's illegal to require a job candidate to take a medical examination prior to a job offer being made. Nor can the employer try to ascertain whether a job candidate has a disability. Therefore it is sometimes up to the employee to decide whether to disclose his or her disability to the employer. The choice is truly the individual's in the case of invisible disabilities. Invisible disabilities are ones which aren't readily obvious to anyone else but yet may keep the individual from performing certain job duties. An example may be a chronic illness like arthritis or a mental illness. While one may have reasons for keeping a disability a secret from an employer, revealing it may require the employer to provide certain accommodations that will allow a worker to perform his or her job.