Judge Mary Yu said the initiative, spearheaded by anti-tax activist Tim Eyman, was "unconstitutional in its entirety."

Eyman had attempted to guarantee everyone in the state flat $30 auto license fees. He promised to appeal Yu's ruling.

The measure, approved in November with a statewide 51 percent of the vote, eliminated a $15 road improvement fee in four counties and killed Sound Transit's motor vehicle tax in parts of King, Snohomish and Pierce counties.

Those opposing the measure, including King and Pierce counties and the city of Tacoma - which sued to stop it from taking effect - argued that it violates the state constitution's single subject rule by linking two subjects: $30 car tabs and a new vote on Sound Transit. Yu agreed.

"Obviously we're fundamentally disappointed with the judge's ruling," Eyman said.

Attorneys for the initiative opponents and for Sound Transit, which gets 20 percent of its budget from the 0.3 percent car tax, contended the initiative promised a new vote on Sound Transit in addition to $30 tabs.

Sound Transit, which joined the lawsuit in December, argued that the measure also jeopardized future transportation plans for the region by eliminating the $15 annual per-vehicle fees charged by Snohomish, King, Pierce and Douglas counties.

Eyman has had little luck with the state Supreme Court.

Two of his previous efforts, I-695 and I-722, were thrown out as unconstitutional for having more than one subject.

However, Mark Kimball, representing the Permanent Offense initiative organization, said I-776 was drafted with the two prior rulings in mind.

"We're optimistic that it will be upheld in the state Supreme Court," Kimball said.