WASHINGTON (Reuters) - The U.S. Supreme Court on Monday threw out an appeals court ruling in favor of a woman’s equal pay claim against a California county because the judge who authored the decision died before it was actually issued.

FILE PHOTO: The U.S. Supreme Court is seen in Washington, U.S., June 11, 2018. REUTERS/Erin Schaff/File Photo

In a unsigned opinion with no noted dissents from any of the nine justices, the high court directed the San Francisco-based 9th U.S. Circuit Court of Appeals to reconsider the case because of Judge Stephen Reinhardt’s death.

The judge, a prominent liberal voice in the federal judiciary for decades, died at age 87 on March 29, 2018. The unanimous 9th Circuit ruling in favor of math consultant Aileen Rizo, who accused Fresno County of paying her less than men who performed similar work, was issued 11 days later.

The Supreme Court faulted the 9th Circuit’s decision to allow Reinhardt to participate in the ruling.

“That practice effectively allowed a deceased judge to exercise the judicial power of the United States after his death. But federal judges are appointed for life, not for eternity,” the high court said.

While the ruling by the 11-judge 9th Circuit panel was unanimous, the judges differed over the legal rationale. The appeals court ruled that salary history cannot be used, whether alone or with other factors, to justify gender-based pay gaps.

The case could yet return to the Supreme Court once the appeals court issues a new ruling.

Pay disparity remains a key issue in the quest for equal rights for women in the United States. Women made 82 cents for every dollar earned by men in 2017, according to U.S. Labor Department data released last year. The department said that in 1979, women’s earnings were 62 percent of men’s earnings and that most of the relative growth in women’s earnings occurred in the 1980s and 1990s, stalling since 2004.

Rizo worked for the Fresno County Office of Education. She sued after discovering in 2012 that her male co-workers were paid more than her, about three years after she started working for the county.

The county said Rizo, who had 13 years of experience, was paid less than her male counterparts based on her prior salary history at the time she was hired, a policy it argued was allowed under a federal law called the 1963 Equal Pay Act. The law barred pay discrimination based on gender.

Under that law, employers can consider certain factors such as seniority when setting pay as long the decision is “based on any other factor other than sex.”

Fresno County said prior salary is not a sex-based factor. Until 2015, it was the county’s policy to set starting employees’ pay based on their past salaries, in part to avoid favoritism and help attract high-quality candidates, according to court papers.

The California legislature in 2016 changed state law so that prior salary cannot be used as a defense to justify gender pay disparities.