California Democratic Party v. Jones
United States Supreme Court
530 U.S. 567 (2000)
California's Proposition 198 replaced the state's closed primary system with an open blanket primary allowing any registered voter to vote for any candidate of any party, overriding party rules restricting primary voting to party members. California's four major political parties (plaintiffs) sued, arguing the law forced them to associate with non-members in selecting their own nominees, violating their First Amendment associational rights; the district court and Ninth Circuit both ruled against the parties, and the Supreme Court granted certiorari.
Whether a state law establishing an open blanket primary, allowing voters of any or no party affiliation to select any party's nominee, violates the political parties' First Amendment right to freedom of association.