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A federal appeals court on Thursday handed down a big win for equal pay advocates by ruling that a Philadelphia ordinance that prohibits employers from asking job candidates about wage history is not unconstitutional.

The precedential Thursday ruling from the U.S. Court of Appeals for the Third Circuit reverses a lower court's holding that the portion of the ordinance banning salary history questions violated employers' First Amendment rights. The appeals court also upheld the lower court's ruling that employers can't rely on salary history in setting wages.

Passed by Philadelphia City Council in 2017, the Wage Equity Law is the city's answer to gender- and race-based pay gaps by helping to "break the discriminatory chain linking an employee's new salary to past salaries and any discriminatory judgments that may have influenced those past salaries," according to Third Circuit Judge Theodore McKee's opinion.

Employers who run afoul of the law are subject to a $2,000 fine and up to 90 days in jail.

In crafting the the ordinance, the City Council relied on testimony and scholarly studies that said, on average, women make 80 cents for every dollar a man in the same position makes. The law was challenged in court by the Philadelphia Chamber of Commerce, which argued that the measure stifles employers' constitutional right to free speech.

U.S. District Judge Mitchell Goldberg of the Eastern District of Pennsylvania agreed with the Chamber that the ordinance violated the First Amendment, ruling that the city had failed to meet the high burden of proof that the law was effective.

But McKee said that Goldberg held the city to a higher standard than was legally required.

"The Supreme Court has not demanded that the enacting authority achieve legislative certainty or produce empirical proof that the adopted legislation would achieve the stated interest even when applying strict scrutiny," McKee said. "Rather, the appropriate inquiry requires courts to determine whether the legislature 'has drawn reasonable inferences based on substantial evidence.'"

He added that the city produced a "plethora" of evidence that a wage gap exists and that existing civil rights laws have been ineffective in closing it.

"In short, the Supreme Court has upheld similar restrictions based on much less evidence than the city presented here," McKee said.

Philadelphia Mayor Jim Kenney praised the ruling Thursday morning.

"I am pleased that the court saw this our way. We enacted this law to help close the wage gap that unfairly affects women and people of color in Philadelphia," Kenney said. "If employers were to keep asking job applicants for salary history, they would simply perpetuate the wage gap. Taking steps to ensure that women and people of color are paid the same as their white male counterparts will have significant social and economic benefits. It is, quite simply, the right thing to do."

Council president Darrell Clarke also said the ruling was a step forward for wage equality.

"I would hope that the business community understands the importance of this issue, as we continue to seek ways to work together to grow Philadelphia's economy for all our citizens," Clark said.

The Chamber did not immediately respond to a request for comment.