On November 19, oral arguments were held in Ravalli County Republican Central Committee v McCulloch, 6:14cv-58. The issue is Montana’s law requiring all qualified parties to nominate candidates for public office in open primaries. See this description, which suggests that U.S. District Court Judge Brian Morris is skeptical of the Republican Party’s case.
UPDATE: here is a second story, although it doesn’t have as much detail as the first story.