This is a clear and direct explanation of the Friedrichs v. CTA case. Many observers think the unions will lose because of the conservative majority in the Court. Ironically, unions hope that Scalia might decide in their favor. The article explains why. 
Somehow it doesn’t seem especially “conservative” to issue a ruling that not only overturns precedent but disrupts labor relations. 
One important issue is free riders, people who don’t pay dues but get benefits. Friedrichs’ lawyers say a ruling in their favor wouldn’t hurt unions, but it is demonstrable that it will.

“The free-rider problem is real and significant. In California and most other jurisdictions, even in right-to-work states where unions operate, unions have a duty to represent and enforce the contractual rights of all employees in a bargaining unit, both members and nonmembers alike.
“Such services don’t come cheap. The fair-share fee for the estimated 9.7 percent of California teachers who, like Rebecca Friedrichs and her co-plaintiffs, have opted not to join their union comprises about 68 percent of full membership dues.
“There is little question that in return they receive a handsome payout. According to figures compiled by The Century Foundation, unionized teachers on average earn an hourly wage 24.7 percent higher than their nonunion counterparts.
“Should Friedrichs and her cohorts prevail in their quest to topple the fair-share system, more teachers no doubt would leave the CTA, reasoning that they could retain the gains of union contracts without paying a dime for them. Public employees in other occupations probably would do the same, believing that they too could free ride without adverse consequences.
“During the oral arguments, attorney Carvin sought to assure the justices that the loss of fair-share fees would have a minimal impact on union membership. The evidence, however, shows that he is dead wrong.
“If the recent labor strife in Wisconsin is any bellwether, a plaintiffs’ victory in Friedrichs could be disastrous for unions and the benefits they deliver. In the aftermath of Gov. Scott Walker’s 2011 assault on public unions and the state’s subsequent implementation of right-to-work policies, for example, the declines in public union membership and dues collected have been monumental.
“The Madison local of the American Federation of State, County and Municipal Employeeshas lost 18,000 of its previous 32,000 members and has seen its annual revenue fall from $10 million to $5.5 million. The state’s largest teachers union, the Wisconsin Education Association Council, has lost more than a third of its members. As the Wisconsin experience shows, free riding isn’t free.”
In the past, Scalia has expressed distaste for free riders, but there is no way of knowing how he will rule now. 
What we can say with some certainty about this case is that it will cripple unions if Friedrichs wins. It will be a blow to a hurting middle class. And it will deepen the economic inequality that is deepening class divisions and harming millions.