Stephen Roberts, with the American Federation of State, County and Municipal Employees (AFSCME), holds up a sign during a rally outside of the Supreme Court Feb. 26, 2018, in Washington protesting a challenge to laws allowing unions representing government employees to collect fees from workers who choose not to join.

Oregon’s public sector labor unions are bracing for an unfavorable ruling from the U.S. Supreme Court on a case that could strike down mandatory public sector union dues that support collective bargaining here and in other states.

But if a similar court ruling in 2014 is any indication, any lost revenue from the change in interpretation of the law could be only temporary.

“There is no way this (ruling) will not impact us, but there is a lot of proof that shows workers will come together to have a voice to make their jobs betters and their communities better,” said Melissa Unger, executive director of Service Employees International Union Local 503.

Justices are scheduled to rule by the end of June on the case of Mark Janus, an Illinois child support specialist, who claims that the mandatory fees violate his First Amendment right to free speech.

With the addition of conservative Justice Neil Gorsuch to the Supreme Court last year, a reversal of existing case law appears likely, according to legal experts.

A decision to strike down the law would reverse a nearly 40-year precedent that the court set in 1977 to permit mandatory fees and deal a blow to public sector unions’ finances and political clout. Twenty-two states, including Oregon and Illinois, allow the mandatory fees. The other 28 states have so-called right-to-work laws, which make the dues voluntary, and have lower participation rates, according to research by a group of scientists who support labor unions and filed an amicus brief against another right-to-work court case in 2016.

But Oregon union leaders say they are optimistic that any negative impact will be only temporary. After decades of diminishing ranks, unions, especially in Oregon, are increasing membership.

The percentage of workers in Oregon who belonged to a union increased from 13.5 percent in 2016 to 14.9 percent in 2017, according to the U.S. Bureau of Labor Statistics.

Given the support for unions in Oregon, labor leaders say they don’t foresee membership falling by significant numbers.

John Larson, president of the Oregon Education Association, pointed to some smaller school districts with voluntary union dues as examples of how the policy change could impact Oregon public sector unions.

While 95 percent of workers covered by OEA are members, membership stands at 90 percent for the David Douglas School District teachers association in Portland, which has voluntary dues, Larson noted.

“I really don’t have that crystal ball to see what happens in the future,” Larson said. “I suppose some people will rethink their membership in the union, but I think the vast majority see the value in membership, see the power of collective action and know that if they stick together, they can provide the schools that students deserve.”

In June 2014, the U.S. Supreme Court ruled in Harris v. Quinn that home care workers who receive public funds as contractors are exempt from the mandatory union fees public sector employees must pay.

With home care workers making up roughly half of its members, SEIU Local 503 saw its dues-paying memberships drop by 5,000 the year of the ruling, from more than 57,000 to more than 52,000. By 2015, however, the numbers had rebounded, and by 2017, membership exceeded 58,000.

“There was a dip, and it came back,” said Jill Bakken, spokeswoman for SEIU 503. “Our home-care side of the union continues to grow even after having gotten this decision. We expect it to be very similar to the Janus decision we now face on the public services side.”

Labor unions approval rating nationally stands at 61 percent, the highest in a decade, according to a Gallup poll released last fall.

Tom Chamberlain, president of Oregon AFL-CIO, attributes the approval rating and boost in membership to the growing income divide despite a booming economy.

“We have an economy today that is rigged against the worker,” Chamberlain said. “You are seeing backlash how things work. Teachers are on strike across the country. They’re fed up with the political process. They want to see real results and haven’t see it.”

The only way to change that income disparity “is to come together with coworkers to make sure they have a voice,” Unger said.