Just in case anyone doubts the potential for this to become law, in the City of Philadelphia you cannot legally carry a knife of any size or type on any street or in any public place unless it is a necessary part of your trade or profession. Minimum penalty is $300 and 30 days.
I found the law. Section
10-820. This law seems to have been enacted as a result of Stanley (utility) knives being used as weapons. The blades on those are only about .75 inches, shorter then even Xacto knives.
(1) Definition.
Cutting Weapon. Any knife or other cutting instrument which can be used as a weapon that has a cutting edge similar to that of a knife. No tool or instrument commonly or ordinarily used in a trade, profession or calling shall be considered a cutting weapon while actually being used in the active exercise of that trade, profession or calling.
(2) Prohibited Conduct. No person shall use or possess any cutting weapon upon the public streets or upon any public property at any time.
(3) Penalty. The penalty for violation of this Section shall be a fine of not less than three hundred (300) dollars and imprisonment of not less than ninety days.
I've been searching for cases involving this statute , but have had very limited luck. The only one I've been able to find is a parolee that got caught with a 3.5" folding knife and a pair of nunchucks. The "Used as a weapon" statute is very vague. Common sense would dictate that keychain SAK's are not "Weapons", but the Cold Steel Recon 1 is. The usual caveat about common sense applies.
**************************************************************************
I think I may also have found the reason that Boston is pushing for the knife control law. In the FBI's UCI for 2010 they took a black eye for a murder rate increase of 47% (50 to 73 homicides) while almost everybody else is decreasing. It's a statistical glitch compared to the total violent crime rate, which actually decreased. But, it's bad press.
http://www.msnbc.msn.com/id/44578241/ns/us_news-crime_and_courts/The polititians may be reacting to that.