The other big decision handed down by the Supreme Court today, explained

Ordinarily, the eight most alarming words to progressives that can appear in a Supreme Court decision are “Justice Alito delivered the opinion of the Court” — and this is especially true in religion cases. Among other things, Alito is the author of the Court’s decision in Burwell v. Hobby Lobby(2014), which gave religious conservatives an unprecedented new ability to ignore federal laws that they object to on religious grounds.

But Alito’s newest opinion, in a case concerning religion in the workplace, does not take sides in America’s culture wars in the same way that he did in Hobby Lobby and similar cases. Indeed, it is a unanimous opinion, joined in full by the Court’s Democratic appointees, that does little more than repudiate a single line in a 1977 Supreme Court decision that virtually everyone thinks was a mistake.

That said, the decision in Groff v. DeJoy announces a new rule that will govern employees who seek an accommodation for their religious beliefs from their employer. Because requests for such accommodations are fairly common, that means that Groff will likely lead to a rush of lawsuits, at least in the short term, as courts try to figure out how to apply Groff’s new rule to individual cases.

Groff’s new rule states that religious accommodation requests should be granted unless they impose a “hardship” on the employer that “would be substantial in the context of an employer’s business.” This highly flexible new rule might potentially be used by far-right judges to give religious conservatives an unfair upper hand in disputes with their employer’s human resources department. Such is the price of vague legal rules.

That said, the actual holding of Groff — that most requests for religious accommodations should be granted, and that an employer cannot dodge this obligation because it might impose minimal costs on the employer — is largely benign. Indeed, it is likely to benefit many employees who make reasonable requests for accommodations that might have been denied under an earlier, less employee-friendly rule.

It will be up to the Supreme Court, in other words, to ensure that Groff does not allow rogue judges to disrupt the workplace. But the actual legal rule announced by Groff is a sensible one that should be applied fairly by most judges.

The Groff case involves a postal worker who wanted to be exempted from working on Sundays because of his religious beliefs. (Although the post office typically does not deliver mail on Sundays, the postal service contracted with Amazon in 2013 to deliver Sunday packages.) The post office claimed that this worker’s request could not be accommodated because he worked in an office with only a few employees, and exempting one of these employees from Sunday work would place too much of a burden on the other workers, who would have to pick up his Sunday shifts.

The Supreme Court, however, did not resolve whether this particular request for a religious accommodation should have been granted. Instead, it sent the case back down to the lower courts to reevaluate this request in light of the Court’s newly announced, more pro-worker rule.

Federal law requires employers to accommodate an employee’s request for a religious accommodation unless granting that request would impose an “undue hardship on the conduct of the employer’s business.” 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.”

This new rule is fairly obviously more in line with what federal law actually says than the old de minimis framework. But, because it is a new rule, and a vague one at that, it is likely to inspire a wave of litigation from employees testing what this new rule means.

And, as noted above, this new rule is likely to inspire some plaintiffs to test whether the courts will take their side in cultural disputes with their employer or a co-worker. As the Groff opinion itself does not say how such cases should be decided, beyond announcing the vague new “whether a hardship would be substantial” test, many employers might face a rough road in the short term, as courts try to figure out how to apply the new rule.

Ultimately, however, such uncertainty is often the price of correcting the Court’s previous errors — and all of the justices agreed that Hardison erred.