Opponents of Washington’s new 9.9 percent income tax filed a constitutional challenge in Klickitat County Superior Court on Thursday — ten days after Governor Ferguson signed the measure. The lead sponsor of the bill called the lawsuit expected and part of the plan.
The Filing
The Citizen Action Defense Fund organized the challenge, retaining former Attorney General Rob McKenna and former state Supreme Court Justice Phil Talmadge as co-counsel alongside the fund’s executive director, Jackson Maynard. Lead plaintiffs Benjamin and Laura Petter own a Chelan County construction business subject to the tax. Additional plaintiffs include a Klickitat County farmer, a Kent trucking company owner, and three industry groups. The Washington Department of Revenue and its director John Ryser are named as defendants.
The Klickitat County venue — a heavily Republican jurisdiction in south-central Washington — positions the case to work upward through the courts. Trial courts are bound by existing state Supreme Court precedent, so a favorable ruling at the superior court level is the expected first step before the case reaches the Supreme Court, likely in early 2027.
The Legal Question
The lawsuit argues that income constitutes property under Article VII of the state constitution, which requires property taxes to be applied uniformly at no more than 1 percent. At 9.9 percent on incomes above $1 million, the plaintiffs contend the law is plainly unconstitutional. The controlling precedent is Culliton v. Chase (1933), a 5-4 ruling that McKenna and Talmadge previously invoked to defeat Seattle’s 2017 municipal income tax. Talmadge said the legislature “has to enact this kind of change in the law by a constitutional amendment.”
The state will contest that framing. Attorney General Nick Brown’s office said it “will be defending the constitutionality of this law in court and expect to prevail.” The state will cite Quinn v. Washington (2023), in which the state Supreme Court upheld the capital gains tax 7-2 as an excise tax. The millionaires tax is written explicitly as a tax on “the receipt of Washington taxable income,” which gives plaintiffs less room to argue around the 1933 precedent.
Senate sponsor Sen. Jamie Pedersen described the challenge as “expected and welcomed,” saying that obtaining judicial review of the Culliton precedent was among the bill’s strategic purposes.
What Comes Next
The Washington Supreme Court is expected to take direct review from the superior court and hear oral arguments in early 2027. Because the tax does not take effect until January 1, 2028, with first payments due in spring 2029, there is no urgency for a preliminary injunction. A superior court ruling is expected this summer.
Five of nine Washington Supreme Court seats are on the November 2026 ballot, meaning the court’s composition could shift before oral argument. Let’s Go Washington, whose referendum petition was blocked in March by the bill’s necessity clause, is pursuing a parallel initiative track requiring roughly 340,000 signatures by June 10.