From Justice Alito's opinion in today's Groff v. DeJoy:
Since its passage, Title VII of the Civil Rights Act of 1964 has made it unlawful for covered employers "to fail or refuse to hire or to discharge any individual, or otherwise to discriminate against any individual with respect to his compensation, terms, conditions, or privileges [of] employment, because of such individual's … religion." As originally enacted, Title VII did not spell out what it meant by discrimination "because of … religion," but shortly after the statute's passage, the EEOC interpreted that provision to mean that employers were sometimes required to "accommodate" the "reasonable religious needs of employees." … [But] EEOC decisions did not settle the question of undue hardship. In 1970, the Sixth Circuit held (in a Sabbath case) that Title VII as then written did not require an employer "to accede to or accommodate" religious practice because that "would raise grave" Establishment Clause questions….
Responding to [this] …, Congress amended Title VII in 1972. Tracking the EEOC's regulatory language, Congress provided that "[t]he term 'religion' includes all aspects of religious observance and practice, as well as belief, unless an employer demonstrates that he is unable to reasonably accommodate to an employee's or prospective employee's religious observance or practice without undue hardship on the conduct of the employer's business."
This thus created a duty on employers to exempt religious objectors from generally applicable rules (e.g., work schedules, dress and hairstyle codes, particular job tasks, etc.) when that can be done "without undue hardship," but what does that mean? The Court's leading precedent interpreting this, Hardison v. Trans World Airlines (1977), has been requiring only accommodations that would involve only "a de minimis cost"—i.e., a very small cost—but the Court's opinion today concludes that this was an offhanded remark that didn't capture the true scope of the Title VII provision:
