A federal judge today upheld Hawaii’s open primary system as constitutional.

The Democratic Party of Hawaii had challenged the open primary in June as a violation of the First Amendment right to free association because all voters — regardless of political party — can participate in choosing the party’s candidates for general elections. The party argued that only voters who are Democrats or who affiliate with the Democratic Party before primaries should be allowed to participate.

U.S. District Court Judge J. Michael Seabright issued a written order that concluded that the party failed to show that the open primary is a “severe burden” on its free association rights and made assumptions about voter behavior without presenting evidence.

Voters approved the state’s open primary system through a 1978 constitutional amendment. The state had a closed primary system between 1968 and 1978.