The Supreme Court yesterday embraced the freedom of association for political parties as it struck down California's "blanket" primary system.

By a 7-2 majority in California Democratic Party v. Jones, the court said that parties have the right to select their own candidates without participation from voters who are members of other parties.

California's blanket-primary system, adopted by state voters in 1996, offers primary voters a single ballot that lists all candidates from all parties — allowing a Republican, for example, to vote for a Democrat for one office and a Libertarian for another.

"Such forced association has the likely outcome… of changing the parties' message," Justice Antonin Scalia wrote for the majority. "We can think of no heavier burden on a political party's associational freedom."

"This decision calls into question the primary system in a majority of states," says Nathaniel Persily of the Brennan Center for Justice. He also said the ruling could limit the ability of states to define party membership or regulate party activities in other ways.

George Waters, lawyer for the parties that challenged the blanket primary, called the decision a victory for the independence of political parties. "The court is saying there are limits to the regulation of political parties," said Waters. "You can't invite the opposing team to help choose your team's leaders."

Only Alaska and Washington state offer as broad a range of crossover primary voting as California. But dissenting justices said the court's ruling could also jeopardize the more common "open" primary system of 21 other states, which allows voters to pick a party on primary day - but then limits them to voting only for candidates from that party.

"There is surely a danger that open primaries will fare no better against a First Amendment challenge than blanket primaries have," wrote Justice John Paul Stevens.

In the majority opinion, Scalia was careful to distinguish blanket from open primaries, noting that in open primaries, a voter affiliates with the party whose ballot he or chooses on primary day. "At least he must formally become a member of the party," said Scalia, who added that the California case "does not require us to determine the constitutionality of open primaries."

Scalia also indicated that a nonpartisan blanket primary — one in which the top two vote-getters go on to the general election, regardless of party — would be more constitutionally acceptable.

But in the extreme case of blanket primaries, Scalia said it is likely that voters antithetical to a party's views will be helping to select that party's candidates. The danger is particularly great for minor or third parties whose members can be overwhelmed by non-member voting.

Supporters of blanket primaries say they increase voter participation and encourage parties to broaden their message. The latter goal, Scalia said, is a "stark repudiation of freedom of political association," because it amounts to the state telling a political party that it must change its message to appeal to a wider audience.

State manipulation of a party's views and candidate choice through the blanket primary, Scalia said, comes at "the critical juncture at which party members traditionally find their collective voice and select their spokesman."

In dissent, Stevens, joined by Justice Ruth Bader Ginsburg, said blanket primaries were acceptable under the First Amendment.

"A state's power to determine how its officials are to be elected is a quintessential attribute of sovereignty," Stevens wrote. "This case is about the state of California's power to decide who may vote in an election conducted, and paid for, by the state."

Tony Mauro covers the Supreme Court for American Lawyer Media and is a legal correspondent for the First Amendment Center.