The Tennessee Republican State Executive Committee will meet on February 7 to vote on whether the party should work for a closed primary for itself. See this story. Tennessee has always had open primaries and has never had voter registration forms that asked applicants to choose a party affiliation or to choose independent status. The Tennessee legislature has a Republican majority in both houses, and the Governor is a Republican, so if the party decides in favor of closed primaries, it would probably work with the legislature, rather than going to court.