Discrimination that is not based on ability to perform the functions of the job, but that is societally necessary (meaning the class of people being denied employment could perform the functions of the job but for some reason, society requires that they not be hired) is justified by:

BFOQ (Bona Fide Occupational Qualification)

Explanation:

In employment law, an employer is permitted to discriminate if the employer has developed a legal and lawful job-related condition/reason for discrimination. This is called a bona fide occupational qualification or BFOQ.

Some examples found by the courts as acceptable reasons to discriminate in hiring:

1. Churches allowed to hire their own members legally and reject others outside their faith.

2. Mandatory retirement age requirements.

3. Islamic bodies allowed to hire their own members and reject others. etc.