New Hampshire Representative David Love (R-Derry) has introduced HB 1166. It would convert primaries from semi-closed to closed. Currently an independent voter may choose a partisan primary ballot on primary day. The bill would restrict primary voters to those voters who had been a member of the party for at least the preceding four months.
If passed, the bill would be unconstitutional as applied to any party that wanted to let independents continue to choose its primary ballot. The U.S. Supreme Court ruled in Tashjian v Republican Party of Connecticut that parties are free to decide for themselves whether to let independents vote in their primaries.
UPDATE: here is the text of the bill. Thanks to Alvin See for the link.