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The Supreme Court ruling Monday against an Illinois requirement regarding union dues for home health aides could ease the way for another, broader legal challenge aimed at teachers unions.

In a 5 to 4 decision Monday, the Supreme Court found that home health-care workers in Illinois cannot be compelled to pay union dues — a practice that the majority said violated the free speech rights of health workers who disagree with the union’s political activity.

Illinois is one of 26 states that require that state employees must pay dues to labor unions to offset the union’s costs for collectively bargaining with the government and creating contracts under which the employees receive pay and benefits.

Monday’s ruling in Harris v. Quinn was limited to home health aides and did not apply to longstanding practices that allow public sector unions to collect millions in dues annually from nonmembers covered by union contracts. In the majority opinion, Justice Samuel Alito wrote that home health aides are not the same as other state employees because they work for individuals in private homes.

Activists behind a lawsuit pending in federal court in California say the Harris ruling has set the stage for their complaint, which challenges the constitutionality of a California requirement that public school teachers must pay union dues regardless of whether they choose to join the union.

In fact, the majority opinion criticized as “questionable” the 1977 Supreme Court decision in Abood v. Detroit Board of Education that gave states the authority to compel public employees to pay union dues.

“Today’s decision is a good sign of things to come,” said Terry Bell, president of the Center for Individual Rights, a conservative law firm that filed the California suit on behalf of Rebecca Friedrichs, a teacher who doesn’t want to pay dues to the California Teachers Association because she disagrees with the union’s political agenda.

In 2011, $178 million of the CTA’s $191 million in revenue came from teacher dues, which can total $1,000 a year per teacher, according to the Friedrichs complaint, which is pending before the 9th Circuit. Pell said he hopes to bring the case to the U.S. Supreme Court sometime next term.

“The court will soon have before it another union dues case, one that asks it to recognize the First Amendment rights of all employees to decide whether to pay union dues, not just home health-care workers,” he said.

Dennis Van Roekel, president of the National Education Association, the country’s largest labor union, blasted Monday’s decision as a setback for workers.

“Americans count on quality public services provided by public employees like educators,” he said. “We need workplaces, including public schools, where front-line employees have a voice. Today’s decision shuts the door on one proven method for ensuring that public sector workers’ voices are heard. At a time when we are just starting to dig out of the worst economic crisis since the Great Depression, we should be creating an economy that works for all of us—not taking radical steps that undermine the rights of public workers while creating uncertainty and instability in the workplace.

If a teacher benefits from a contract negotiated by a union, the teacher should share the cost, he said.

“Every educator who enjoys the benefits and protections of a negotiated contract should, in fairness, contribute to maintaining the contract,” Van Roekel said. “And fair share simply makes sure that all educators share the cost of negotiations for benefits that all educators enjoy, regardless of whether they are association members.”

If the Friedrichs case goes forward, it will be the second high-profile legal assault on teachers unions in recent months. Earlier this month, a Los Angeles judge struck down teacher tenure and other California laws that offer job security to educators, a move that has encouraged activists in other states to consider similar legal challenges.