It’s been two months since the Supreme Court handed Gov. Bruce Rauner a huge victory in a landmark case that curtailed the power of public-sector labor unions.

The 5-4 decision in the case of Mark Janus versus AFSCME Council 31 may have started in Illinois, but the ruling had national implications — though the full extent isn’t yet clear.

“It’ll certainly take a while to determine” the impact, said Robert Bruno, a labor expert who teaches at the University of Illinois at Chicago.

Hard numbers don’t yet exist, but by next year, filings with the federal Department of Labor will show any effects on Illinois’ major labor unions, he said.

Public-employee unions are legally obligated to represent all workers in the bargaining unit — such as in grievances or to protect employee rights in other workplace issues — whether or not those employees are dues-paying members.

But employees who chose not to join the union still had been required to pay “fair share” fees, sometimes called “agency fees,” to cover costs for representing them; such fees, which were lower than full dues, didn’t include the cost of the union’s political or lobbying efforts.

In his lawsuit, Janus went to court, arguing that even that lower amount meant he was unfairly required to support an organization he disagreed with politically — and in its ruling, the court agreed.

The 83-page majority opinion, written by Justice Samuel Alito, declared that “states and public-sector unions may no longer extract agency fees from nonconsenting employees.”

As a result of that ruling, Bruno’s research has predicted an 8 percent loss for Illinois’ total public sector unions, with teachers’ unions faring slightly better.

Three Chicago Teachers Union members have asked to stop paying dues that average about $1,000 annually, CTU organizer Martin Ritter said. That’s out of about 25,000 members — a group that includes some recently added members who teach at charter schools, which are privately managed but publicly funded, including some recently added privately managed charter school teachers.

Of the 2,300 people, who as of last September paid “fair-share” or “agency” fees of about $750 a year, 300 remained on the CTU’s rolls in June, Ritter said. The rest signed union cards.

More than half of the 300 — such as maternity leave fill-ins, beginning teachers — aren’t returning to CPS jobs at all.

“We had a vigorous plan to organize and sign up all CPS employees covered by our bargaining unit, as well as continuing to expand” unionizing charter school teachers, Ritter said.

“Our union will be growing this year,” he said, referring to several hundred new clinicians, case managers and teachers for oversized classes CPS has vowed to hire.

Cook County has stopped deducting fair share fees from 730 fee-paying employees as a result of the ruling, said Frank Shuftan, a spokesman for county board president Toni Preckwinkle. Of the county’s 22,000 employees, about 18,000 are in unions.

Shortly after the ruling, Illinois’ Central Management Services Department emailed all state employees saying the state would stop deducting the fees from paychecks of non-union members — about $737 per person annually — with member dues at about $911 per member.

“Payroll’s first priority, per the court’s determination, is to ensure that all Fair Share employees’ agency fees cease being deducted from their checks,” CMS spokesman Mike Deering said in an email. “Until that’s accomplished, we cannot provide a full accounting as to how many full union members changed their status to non-membership.”

The American Federation of State County and Municipal Employees said “several dozen” former members had dropped out. Spokesman Anders Lindall said just 10 percent of the 75,000 public service workers represented by the union were fair-share payers.

Lindall, too, said “more than 1,000” fee-payers signed up as new dues-paying union members.

“That’s encouraging. At the same time, we’re acutely aware that the powerful forces who funded the Janus case are determined to destroy the labor movement and drag down working people,” Lindall said in a statement.

Lindall said the union is aware it’s only the beginning.

“The other side’s full assault hasn’t yet been launched,” he said. “In the meantime, we’re going to keep working hard every day to sign up more former fee payers and build our union stronger than ever.”

DISCLOSURE: Some unions have ownership stakes in Sun-Times Media, including the Chicago Federation of Labor; Operating Engineers Local 150; SEIU Healthcare Illinois-Indiana and SEIU Local 1.