Former WA AG Rob McKenna gears up for legal fight against millionaires' tax

McKenna says courts have been clear: income is property, and the millionaires' tax won't survive

Mar. 31, 2026 at 2:05am

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A detailed, photorealistic painting of a solitary briefcase or legal document sitting on a wooden desk, with warm, golden light streaming in through a window and casting deep shadows across the scene, creating a contemplative, cinematic mood.The legal battle over Washington's new millionaires' tax takes center stage, with former AG McKenna leading the charge against what he sees as an unconstitutional tax on personal income.McKenna Today

Former Washington State Attorney General Rob McKenna is leading the legal battle against the state's new millionaires' tax, which was signed into law on Monday. McKenna is preparing to file a lawsuit with the Citizen Action Defense Fund, arguing that the tax is unconstitutional because income is considered property and must be taxed at a uniform rate.

Why it matters

The millionaires' tax is a controversial new law that aims to generate additional revenue for the state, but McKenna believes it will be overturned in court based on previous rulings that have found income to be a form of property.

The details

McKenna says the Superior Court is bound by precedent that has consistently defined income as property, and therefore the millionaires' tax will be declared unconstitutional. He notes that a similar case he brought around five years ago was overturned after the King County Superior Court found the income tax to be unconstitutional, a decision that was upheld by the Court of Appeals and ultimately not reviewed by the state Supreme Court.

  • The millionaires' tax was signed into law on Monday, March 31, 2026.
  • McKenna is preparing to file the lawsuit with the Citizen Action Defense Fund 'very soon'.

The players

Rob McKenna

Former Washington State Attorney General who is leading the legal battle against the state's new millionaires' tax.

Bob Ferguson

The current Washington State Attorney General who McKenna says is hoping the state Supreme Court will decide that income is not property, and therefore the progressive income tax is constitutional.

Citizen Action Defense Fund

The organization that McKenna is preparing to file the lawsuit against the millionaires' tax with.

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What they’re saying

“It will be filed very soon, and it will go to a superior court in Washington, which will declare that this tax is unconstitutional, because the Superior Court is bound by all of this Supreme Court precedent, not just the 1933 case, but all the other cases that have found that income is property, and the court will probably note for itself, 'Oh, yeah, looking at this definition, how do you say income isn't property? If everything tangible and intangible is subject to ownership?' The Superior Court doesn't get to rewrite precedent, right? They are bound by precedent.”

— Rob McKenna, Former Washington State Attorney General

“The assumption that the proponents of this tax are making is that the Supreme Court will grant direct review, and then they will suddenly decide that, notwithstanding that incredibly broad definition of property, somehow income is not your property. The hope is, on the part of the proponents, apparently, including Governor Ferguson, that the Supreme Court will decide income is not property, and therefore this progressive income tax is fine.”

— Rob McKenna, Former Washington State Attorney General

What’s next

The judge in the case will decide in the coming weeks whether to grant McKenna's request for a temporary injunction to block the millionaires' tax from taking effect while the legal challenge proceeds.

The takeaway

This case highlights the ongoing legal battle over the constitutionality of income taxes in Washington state, with McKenna confident that the courts will once again rule that income is a form of property that cannot be taxed in a non-uniform manner.