Labor leaders and their allies were thrilled when a Wisconsin judge ruled on Friday that the state’s year-old right-to-work law – signed by Governor Scott Walker – violated the state’s constitution .

Related: Wisconsin right-to-work law struck down by court as unconstitutional

But several law professors predicted that the Wisconsin supreme court, on which conservative justices have a commanding 5-2 majority, would ultimately overturn the lower court judge’s decision and rule that the law does not violate the state constitution.

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Walker and Wisconsin’s Republicans consolidated conservative control of the state supreme court last Tuesday when Rebecca Bradley – an outspoken conservative whom Walker had appointed to fill a vacancy left by a justice’s death – won a full 10-year term in a 53% to 47% vote. She was helped by $2.6m in spending from outside groups.

On Friday, William Foust, a state judge in Dane County, which includes Madison, ruled that the state’s right-to-work law was an unconstitutional taking of union property because it required unions to provide benefits to workers who didn’t pay any union dues or fees.

Paul Secunda , a labor law professor at Marquette University in Milwaukee, said he strongly agreed with the ruling. Then he added: “Will it be upheld? Absolutely not. It will be overturned by a very partisan Wisconsin supreme court, especially with this week’s election of a fifth conservative justice.”

When Walker signed the law in March 2015 , it made Wisconsin the 25th state to adopt right-to-work, which bars any requirement that workers at unionized workplaces pay union fees. Unions are required to provide these non-payers – unions call them “free riders” – regular union services, such as representing them when they have grievances.

In the past five years, Indiana, Michigan and West Virginia have also enacted such laws, with Republicans championing them as measures that advance employee freedom and improve states’ business climates. Unions denounce these measures, saying they encourage free riders and are designed to undercut labor’s strength, membership and finances.

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Business groups attacked Friday’s ruling and predicted that it would be overturned. Scott Manley, senior vice-president of government relations with Wisconsin Manufacturers and Commerce – the state’s leading business group – said: “The judge’s ruling is an act of blatant judicial activism that will not withstand appellate review. Judge Foust came to the absurd and legally untenable conclusion that labor unions have a property right to the wages of workers.”

Walker agreed, writing on Twitter: “We are confident Wisconsin’s freedom-to-work law is constitutional and will ultimately be upheld.”

Kenneth Dau-Schmidt , a labor law professor at Indiana University, noted that in 2013 an Indiana judge had declared that state’s right-to-work law flouted the state constitution’s takings provision. But the Indiana supreme court upheld the law.

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Dau-Schmidt said a stronger case could be made under Indiana’s constitution than under Wisconsin’s that right-to-work is unconstitutional.

“Our Indiana constitution says you cannot compel the provision of services without compensation,” he said. “Our takings clause is broader in that it expressly mentions services.”

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He forecast that the Wisconsin supreme court would uphold the right-to-work law, saying the court was generally more partisan than Indiana’s.

Wisconsin unions cheered Friday’s ruling – it was a bright spot for labor after Walker’s five-year offensive, the governor having enacted a landmark law in 2011 that all but ended collective bargaining for public-sector unions.

Responding to Foust’s ruling, Phil Neuenfeldt , president of the Wisconsin State AFL-CIO, said: “The courts put a needed check on Scott Walker’s attacks on working families. Right-to-work goes against the Wisconsin principles of fairness and democracy and hurts all of Wisconsin by eroding the strength of our middle class.”

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Henry Farber, a labor economist at Princeton, found in a study that right-to-work laws, by allowing “free riders”, shrink union treasuries. Another study concluded that the percentage of free riders in right-to-work states ranged from 9% in Georgia to 39% in South Dakota.

In another study, David T Ellwood, a professor at the Kennedy School of Government at Harvard, and Glenn A Fine, a former Justice Department official, found that in the five years after states enacted right-to-work provisions, the number of unionization campaigns fell by 28%, and in the next five years by an additional 12%.

Secunda predicted that Wisconsin’s right-to-work ruling would mobilize conservatives and union supporters alike in this autumn’s elections. He predicted that the ruling would ultimately prove a “wash” in terms of which party was helped more.

Dau-Schmidt added: “In Wisconsin, this could certainly get people riled up. I think the gloves are off. Labor realizes that Republicans are out to smack them up. It’s not just that labor is down – they’re really looking for the extirpation of organized labor.”

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Secunda saw one silver lining for labor.

“At the very least,” he said, “this puts a spotlight on the idea that there are free riders who are taking advantage of union services without having pay for them.”

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