In Knox v. Service Employees Int' Union, Local 1000, the SEIU imposed a special assessment on all employees which it represented -- union members and non-members alike -- in order to fund a special campaign to defeat Propositions 75 and 76, which were part of Arnold Schwarzenegger's 2005 attempt at public finance reform.
The non-members brought a class action alleging that this violated prior Supreme Court precedent holding that a public sector union cannot charge non-member employees for the cost of its political activities without first giving them prior written notice and an opportunity to opt out of the payments (i.e., so-called "Hudson Notice"). The Court agreed.
The result itself was pretty obvious. But what was really interesting about the decision is the extent to which the Supreme Court laid the groundwork for a future decision that might strip unions of the right to make coerced political contributions from non-members. For example, the Court first explained that imposing mandatory charges for political purposes inevitably raises serious First Amendment concerns:
When a State establishes an “agency shop” that exacts compulsory union fees as a condition of public employment, the dissenting employee is forced to support financially an organization with whose principles and demands he may disagree. Because a public-sector union takes many positions during collective bargaining that have powerful political and civic consequences the compulsory fees constitute a form of compelled speech and association that imposes a “significant impingement on First Amendment rights.”
In contrast with this impingement on employee constitutional free speech rights, the Court noted that "“unions have no constitutional entitlement to the fees of nonmember-employees” and their “collection of fees from nonmembers is authorized by an act of legislative grace . . . that we have termed “unusual” and “extraordinary.” Interestingly the Court then cast doubt on the continuing validity of the precedents allowing such political deductions under certain circumstances as an "anomaly" that may violate the First Amendment.
By authorizing a union to collect fees from nonmembers and permitting the use of an opt-out system for the collection of fees levied to cover nonchargeable expenses, our prior decisions approach, if they do not cross, the limit of what the First Amendment can tolerate.
Thus, while the SEIU's political charges were easily struck down because they were not preceded by notice and a right to opt-out, the Court clearly implied that even these procedural protections may not be enough to justify such deductions in the future.