I lived in Manhattan for the past 10 years and just moved to AZ about 4 months ago (yes I am in firearm heaven).
I carried a Spyderco Delica religiously for the past 5 years and never had any issues. It is a lockback, under 3" and cannot be flicked open with one hand. Further, in NYC you cannot have the clip exposed as the entire knife must be concealed - carried it at the bottom of my right front pocket. I have gone through security at court houses and the WTC memorial with my Delica and it was never once a problem.
AS with fixed blades - YES YOU CAN CARRY THEM. As long as they are under 3" not double-edged and concealed, it is a non-issue. I always kept an ESEE3 in my EDC bag and had my bags searched a few times at random subway stations. It was never an issue. I have also carried an ESEE Izula in my pocket with no issues.
I would stay away from Benchmades with the axis lock as a cop MAY consider that a gravity knife as it can be flicked open. If you really want to be safe, carry a SAK or leatherman.
Realistically, carry what you like and dont give the cops a reason to search you. Even with a SAK, you may get a dick cop who just wants to be an a-hole and give you problems.
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