Illinois state law allow medicaid patients to hire personal assistants (PA) to take care of them at home. The state pays for the PA while the patient hires, fires, supervises, interacts and fires PAs. The state also allow for PA's unionization and Illinois fair-share provision require PAs to pay a fee to unions whether they join or not. Pam Harris were among a group of PAs were hired by their relatives to provide in-home care services and challenge the fair-share provision.
Are requiring PAs to pay a union whether they want to join or not constitutional?
No, 1st Amendment prohibits collecting union fees from PAs whom don't wish to support or join.
State argued that collecting fees from nonunion employees prevent employees from being free-riders. The PAs argued that they are not full-fledged employees of the state nor being served by the employees. PAs don't receive representation from union when there's a dispute with the patients because they are quasi-private employees. Thus, the state's free-rider argument is insufficient to overcome 1st Amendment freedom from conform to a union's ideology.
As explained on CNN, this is a limited defeat for the Unions. This Ruling applies to home-health care workers. This ruling does not apply to all unionize employment and limited fees may be taken from workers from employees who work at unionized jobs given it's not a right to work state. Right to work means an employee may opt out of the company union. As the Court's dissenting opinion noted that the Court has a 40 year history of allowing limited fees to be taken to prevent free-riders. But as the majority pointed, the PAs are not free-riders because they weren't serve by the union.