The 9th U.S. Circuit Court of Appeals (search) on Monday struck down Washington state's "blanket" primary system, saying it violates the right of political parties to have their own members choose candidates for office.

In a 3-0 decision, a panel of the court cited a 2000 U.S. Supreme Court decision that ruled a similar system in California unconstitutional.

Washington's system, adopted in 1935, allows voters to pick nominees from any political party or even to mix and match -- picking a candidate for governor from one party and a candidate for secretary of state from another, for example.

Judge Andrew J. Kleinfeld (search wrote that that violates the parties' right to choose their own nominees.

"The right of people adhering to a political party to freely associate is not limited to getting together for cocktails and canapes," Kleinfeld wrote. "Party adherents are entitled to associate to choose their party's nominees for public office."

The state Democratic, Republican and Libertarian parties challenged the law, filing suit against Secretary of State Sam Reed (search). The Washington State Grange (search), which sponsored the blanket primary system, intervened on Reed's behalf.

U.S. District Court Judge Franklin Burgess ruled in March 2002 that Washington could keep its system, saying Washington and California's blanket primaries are significantly different, and that Washington's political parties had failed to show they had suffered any harm.

In California, he noted, voters register by party, while in Washington, they do not.

Burgess said the blanket primary is "a constitutional exercise of the state's power to regulate elections."

The 9th Circuit panel disagreed, saying any attempts to differentiate California's system were "distinctions without a difference," and that the parties did not need to show they had been harmed by Washington's system.

Kleinfeld wrote that it doesn't matter whether Washington state registers voters by party.

"That the voters do not reveal their party preferences at a government registration desk does not mean that they do not have them," he wrote. "The Washington scheme denies party adherents the opportunity to nominate their party's candidate free of the risk of being swamped by voters whose preference is for the other party."

In defense of the system, the state's attorneys argued that maintaining it was a compelling public interest because it encouraged greater participation in the nominating process.

Also, they argued, the winners of the primaries are "the 'nominees' not of the parties but of the electorate."

The judges said that was the problem with the system, not a defense of it.

"Put simply, the blanket primary prevents a party from picking its nominees," Kleinfeld wrote.