42 U.S. Code § 2000e-2 allows for an employer to discriminate against employees and potential employees "on the basis of his religion, sex, or national origin in those certain instances where religion, sex, or national origin is a bona fide occupational qualification reasonably necessary to the normal operation of that particular business or enterprise." It is important to note that this exemption from employment discrimination liability does not allow the employer to discriminate on the basis of race.
Bona fide occupational qualifications are present in other federal statutes as well. The Age Discrimination in Employment Act (ADEA) was enacted to prevent age discrimination in the workplace. The ADEA does contain a bona fide occupational qualification exemption, and the ADEA also requires that the age discrimination must be “reasonably necessary to the normal operation of the particular business.”
Bona fide occupational qualifications typically are invoked when an employer has been accused of employment discrimination. The employer may use the defense that the discrimination was based on a bona fide occupational qualification. Bona fide occupational qualifications are often used for safety reasons, such as imposing a mandatory retirement age for airline pilots and bus drivers.
For more on bona fide occupational qualifications, see this University of Cincinnati Law Review article, this Louisiana State University Law Review article, and this Journal of Business Studies Quarterly article.