In a ruling issued Thursday, the Supreme Court clarified that employers may refuse to make religious accommodations.

In his unanimous opinion, Justice Samuel A. Alito Jr. found that employers had to show that such accommodations would result in “substantial increases costs” for the business.

Alito wrote in a letter that the justices were “brushing aside” an incorrect interpretation from a prior Supreme Court case involving Title VII of Civil Rights Act. He noted that a group of diverse religious organizations argued that the interpretation “bless[ed] the denial in many cases of minor accommodations, making it more difficult for members of minority religions to enter into the job market.”

Gerald Groff was a rural Pennsylvania mail carrier who, invoking his Christian faith, quit the job rather than deliver Amazon packages during Sundays. He sued the U.S. Postal Service for discrimination.

The U.S. Court of Appeals, 3rd Circuit, ruled in favor of the Postal Service, citing a landmark 1977 Supreme Court decision, Transworld Airlines, Inc. v. Hardison, that found employers were not required to endure “undue burden” in order to accommodate their employees’ religious observance.

Groff claimed in court documents that the 1977 ruling weakened the religious rights that Congress intended to protect through the 1972 amendments of the Civil Rights Act.

Alito, in his ruling, wrote that the 3rd Circuit Court and other lower courts interpreted the term “undue burden” as any cost or effort greater than “de minimis”.

Alito wrote that this interpretation was “erroneous” and may have led courts to not pay enough attention to the actual meaning of Title VII in relation to a number of recurring issues.

The opinion says: “We believe it is sufficient to say that a company must demonstrate that the burden of providing an accommodation would result substantially in increased costs for the conduct of their particular business.”

The Supreme Court ruled that employers must accommodate workers’ religious practices in a reasonable manner. “Not just to assess the reasonableness or otherwise of any particular accommodation.”

This distinction is important. The court said that an employer would need to consider other options, such as voluntary shift swapping, when faced with an accommodation request. The court ruled that employers should also consider other options such as voluntary swapping of shifts.

In briefs filed for the case, some congressional Republicans had supported such an interpretation.

The Biden Administration had argued the court should let Congress decide the issue, as they have spent decades evaluating and rejecting higher standards to accommodate religious employees.

The Justice Department informed the justices that the Groff had asked the court to “do what Congress wouldn’t” by rewriting law.

According to the Biden brief, the existing law provides too little protection to religious workers. However, “that argument should go to Congress who is better placed to weigh competing interests and strike an appropriate balance in this sensitive field.”