Most states have Firearm Preemption Laws. Laws that generally "prevent local jurisdictions from imposing ordinances more restrictive than laws passed by the state legislature and, in some cases, rescind local ordinances to ensure uniform firearm laws statewide." http://www.nraila.org/Issues/factsheets/read.aspx?ID=48
In 2010, State Rep. Jenn Coffey sponsored and helped pass a bill to remove state regulations on knifes in NH (except for felons.) This year, she sponsored and helped pass a bill to create a knife preemption law to prevent local governments from regulating knifes.
Rep. Coffey also endorsed Ron Paul for President. She is doing great work.