Sen. Lisa Brown brought a lawsuit to invalidate the state's two-thirds vote requirement for tax increases, which was adopted by Initiative 601 in 1993. The case started in 2008 when Sen. Brown filed a writ of mandamus against Lt. Gov. Brad Owen after he declined to approve a tax increase bill that did not receive the required two-thirds vote. Sen. Brown argued the supermajority vote requirement was unconstitutional under Art. II, Sec. 22 of the Washington Constitution.
The Supreme Court unanimously ruled against Sen. Brown today in an opinion by Justice Mary Fairhurst, saying that the judiciary cannot interfere in an internal legislative process. The court declined to address the constitutionality of the supermajority vote requirement.
The unanimous decision is especially significant considering previous statements by Chief Justice Alexander and Justice Chambers (he of the "elephant in the court" opinion) that revealed their dislike of I-601. I would have expected at least a dissent or concurring opinion in the Brown case.
Case documents and timeline can be found here.
(Note: Publishers of this blog filed an amicus brief in support of the state in this action.)
UPDATE: Kris Tefft at AWB applauds the ruling, Jason Mercier at WPC wishes he had put down money on his predicted outcome, and Andrew Villeneuve at NPI suggests that the legislature and Gov. Gregoire could force the constitutionality issue with an act of "cooperative civil disobedience." The Amateur Law Prof calls it a "stunning punt." My own analysis can be found here.