Chicago Tribune:

Losing the required fees worries labor leaders because it could lead to more workers leaving unions to avoid the cost, starving unions of money and members. The American Federation of State, County and Municipal Employees union at the center of the lawsuit called it "yet another example of corporate interests using their power and influence to launch a political attack on working people and rig the rules of the economy in their own favor."

A similar case out of California was already in the legal pipeline when Rauner acted in 2015. By the time it was decided, the Supreme Court was short one member following the death of conservative Justice Antonin Scalia. The court issued a 4-4 split decision that left the existing system intact.

With President Donald Trump's appointment of Neil Gorsuch, the court's ruling in the Illinois case could deal a major blow to public-sector unions nationwide if Gorsuch sides with the conservative justices who were in favor of doing away with the "fair share" fees.

Unions negotiate new contracts and handle grievances on behalf of all workers within a bargaining unit, not just those who are members. The fees help pay for those efforts.

Illinois is one of about two dozen states that requires its workers to pay fair share fees to public employee unions even if they are not union members. The thinking is that workers who are not part of a union still benefit from its services, even if they don't support the union's political agenda. If the fees were no longer required, more workers might decide not to join unions in an effort to keep more money in their paychecks.

Rauner has contended that the fair share system violates free speech and that workers should not have to support unions they don't want to belong to. Unions are not allowed to spend fair share fees on political activities such as campaign contributions, but the governor has questioned that restriction, saying it's impossible to separate political activities because public-sector unions negotiate directly with the government.

"By its very nature, the activity of a government union is political," Rauner said in a Thursday interview with the Tribune. "Everything they do is political because it's inside government, it impacts politics."