But why would the locking folder law refer to folders over 4" when everything over 4" is already illegal? And I've heard this directly from the mouths of 2 shop managers who had their locking knives confiscated.
Just because property is confiscated by law enforcement doesn't mean the property was illegal. Sometimes law enforcement personnel violate the 4th amendment and unlawfully confiscate property, and sometimes they do it at the behest of District Attorneys. Members of law enforcement will often gamble with violations of the constitution by assuming that most people don't know their rights and won't complain for fear of getting into trouble, or that most people can't or won't hire a lawyer to sue and fight the confiscation. It is an unfortunate fact in this country that people in positions of power (like law enforcement) often abuse their power and in the process violate peoples constitutional rights, and they often get away with it.
Take the clip off so you're never tempted to clip it
I think this is great advice, and I will take it one step further-
Some cops are dishonest and might be willing to lie just a little to bolster a case. If you are in NYC and get stopped by a cop, and if that cop finds you carrying a knife with a pocket clip attached, even if the knife was being carried in a completely concealed manner, the cop could lie in court and say that he saw the knife clipped to your pocket, and that the sight of the clip gave him a lawful reason to stop the you.
Since there is in fact a clip attached to the knife, the presence of the clip would bolster the cops story that the knife was in fact clipped to your pocket, and a jury might consider the presence of the clip to be enough evidence to believe the cop. But if there is no clip attached to the knife, it would be impossible for a dishonest cop to lie and say that the knife was clipped to your pocket.
My attorney often advises me to conduct myself as though every cop is dishonest. He tells me " Give the cops as little opportunity as possible to tell plausible lies against you in court". Naturally it is impossible to completely protect oneself from the lies of dishonest cops, but removing a pocket clip is a very easy thing to do, and it's not like you want to use that clip in NYC anyway.
On a different issue, I would not advise telling a cop that you are carrying a knife for work unless you can in fact back up that story. Let's say that you are visiting NYC or that it's your day off from work and you tell a cop that you are carrying the knife "for work", technically, you have just lied to a cop (which is a crime) and that lie could be proven to be a lie later in court if you are arrested. And if you find yourself facing a jury, charged with a weapons offense, you don't want the cop taking the stand and testifying that you LIED to him, and you don't want the prosecutor to continually remind the jury that you LIED to the officer. Prosecutors LOVE to catch defendants in a lie because it gives them many opportunities to question your honesty, your character, and your true motives for carrying a knife. Imagine the prosecutor telling the jury "Why would the defendant LIE about his reason for carrying a knife? Clearly he was up to no good".
Here are a few suggestions, if you carry a bag of some sort, carry an apple. If a cop asks you why you are carrying the knife, you can say "To cut my apple". Or, if you have a reason to carry pencils, carry a few pencils that you clearly sharpened with a knife (the tip of a pencil sharpened with a knife has a distinctive look), and if a cop asks why you are carrying the knife, say it's for sharpening your pencils. These are both plausible stories, and there is no way to prove that they are untruthful.