At least, that's how the opinion in the long-lingering challenge to the Legislature's 2005 session abuse of I-601 appears to read. In 2006 lawmakers amended the way the state spending limit was calculated to validate actions taken the prior year. There's a five member majority opinion and four concurrences. This is from the majority opinion.
The state expenditure limit is a creature of statute, as are the laws that govern its calculation. The legislature is free to amend the expenditure limit and the process by which it is calculated. The legislature exercised this prerogative when it enacted the 2006 amendment. When the legislature enacts laws, it speaks as the chosen representative of the people.
Retroactivity is explicitly fine, too.
It is undisputed that the legislature intended the 2006 amendment to operate retroactively.
Postman has a good account.
The Washington Policy Center offers its perspective.
The Evergreen Freedom Foundation, which was a party to the lawsuit, has terse comment.
Update Weird formatting glitches fixed.