Sections 501 and 505 of the Rehabilitation Act of 1973
This law makes it illegal to discriminate against a qualified person with a disability in the federal government. The law also makes it illegal to retaliate against a person because the person complained about discrimination, filed a charge of discrimination, or participated in an employment discrimination investigation or lawsuit. The law also requires that employers reasonably accommodate the known physical or mental limitations of an otherwise qualified individual with a disability who is an applicant or employee, unless doing so would impose an undue hardship on the operation of the employer's business.
Source: U.S. Equal Employment Opportunity Commission