Early in December 2015, the Virginia Republican Party decided that voters who ask for a Republican presidential primary ballot in March 1, 2016, must sign below a statement that says, “My signature below indicates I am a Republican.” See this story. Virginia does not have registration by party.
Some years ago the party considered asking voters in its primaries to sign below a statement that the voter intends to vote Republican in the upcoming general election, but that idea was dropped.