I am unclear on US law (obviously) but in Belgium, the act of using it as a weapon can turn any object into an illegal weapon. A kitchen knife used for cooking is not a weapon. A kitchen knife carried concealed into a football stadium can be classified as an (illegal) weapon. A lot depends in intent, and judgment of the officer(s) involved.
I have 2 pocket knives. A spyderco delica and a swiss army knife (multitool) which is used as a keychain for the keys of the server / comms racks. I often carry both. Both are locking blades of identical length. But the swiss knife would not get a second glance from an officer in most settings (it is a known and often encountered item) whereas my spyderco would raise serious questions and potentially get me fined or arrested if I'd take it where police have a reason to suspect wrong intent. The only reason is that the spyderco 'looks' dangerous.
I'd love to carry a spyderco civilian, but the simple fact of carrying it would land me in heaps of trouble unless I could reasonably claim I have a legit, 'non-weapon-use' reason for carrying it. Belgian law does not put restrictions on bladed weapons (other than a couple of specific items) but intent to use as a weapon is not allowed. The reason for this is that there are plenty of scenarios where something is not meant to be a weapon, yet the same item in another setting is.
This means that a general purpose knife is generally allowed unless there is reason to suspect violent intent. A knife intended to be a weapon otoh has intent tacked on by default unless there is a reason to assume otherwise.
