The gist:

Nearly half a century ago, however, in Trans World Airlines v. Hardison (1977), the Supreme Court announced that an “undue hardship” exists if accommodating such a request would require an employer to “bear more than a de minimis cost.” The Latin phrase “de minimis” refers to a burden that is so small or trifling as to be unworthy of consideration.

Pretty much everyone involved in this case, including all nine justices, agree that this “more than a de minimis cost” standard is wrong. As Alito writes, “in common parlance, a ‘hardship’ is, at a minimum, ‘something hard to bear.’” So an employer shouldn’t be able to show an undue “hardship” merely by showing that they will be hit with a trifling expense.

Groff repudiates this much-loathed line from Hardison. And it replaces Hardison’s “more than a de minimis cost” framework with a new rule, which requires courts hearing cases about religious accommodations to ask “whether a hardship would be substantial in the context of an employer’s business in the commonsense manner that it would use in applying any such test.”