The U.S. Supreme Court ruled earlier this week that an Idaho law banning local government employers from allowing payroll deductions for political activities does not violate unions' First Amendment free speech rights. You can download the opinion here: Ysursa v. Pocatello Ed. Ass'n, U.S., No. 07-869, 2/24/09).
The Idaho Voluntary Contributions Act, enacted in 2003, prohibited public employees' unions from using payroll deductions to fund political activities, defined as “electoral activities, independent expenditures, or expenditures made to any candidate, political party, political action committee, or political issues committee or in support of or against any ballot measure.” A group of unions representing state and local employees in the state sued to challenge the VCA on the basis that it unlawfully restricted unions' First Amendment Right.
A 6-3 majority of the Supreme Court held that the VCA does not violate unions' rights: “Idaho's law does not restrict political speech, but rather declines to promote that speech by allowing public employee checkoffs for political activities,” Chief Justice Roberts wrote for the majority. Applying rational-basis review, he found that the restriction “is reasonable in light of the State's interest in avoiding the appearance that carrying out the public's business is tainted by partisan political activity.”
With that endorsement, don't be surprised if more states (particularly right-to-work states) pass similar legislation.