First let me point out that I have lived in California (San Diego) for almost 45 years now, and I have been openly carrying a fixed-blade here for over the past ten years, so for me the laws regarding this issue are not academic, but instead, they are a very real concern. For that reason I make a point of knowing the laws on such matters and I have a lawyer on retainer who, among other things, advises me on knife laws.
When considering knife laws it is important to understand that there is
the law, the written penal codes, and then there is the
perception of law enforcement. Even if something is completely legal according to the penal code, it's still possible that a cop will arrest you because they
perceive your knife, or manner of carry, to be illegal. And if your knife or manner of carry are not specifically mentioned by the law, then you fall into what I would call a
grey area, and that might increase your chances of being arrested. If you are arrested, the charges might be quickly dropped a few hours later, but it might also take a few days, or weeks. It's also important to know that prosecutors are always looking to push the envelope in their pursuit of a conviction, and that they will always interpret the law in a way that is least favorable to you. These are important things to remember whenever venturing into a
grey area of the law. And because California law is not micro-specific regarding what constitutes a "concealed" fixed-blade, that leaves some grey area.
As far as how CA law defines "concealed" fixed-blades, here is a link to CA penal code 21310 from California's official government website-
http://leginfo.legislature.ca.gov/faces/codes_displaySection.xhtml?lawCode=PEN§ionNum=21310. Unfortunately the wording is a little vague, but it does specifically define "concealed" as being "concealed upon the person". I will also mention that under California law, ALL fixed-blades regardless of design are considered "dirks and daggers".
As far as a fixed-blade being covered by clothing, as my lawyer explained to me, whether or not the knife is considered "concealed" under the law will generally be determined by the perceived INTENT of the person carrying the knife. If a prosecutor believes that you were intentionally trying to conceal the knife from view, then you could expect to be charged. However, if the knife were accidentally covered by an article of clothing, then that should not be considered "concealed" under the law because it was not the persons INTENT to hide the knife from view (There is case law directly on this point in California, but I forget the case at the moment. As I recall, a man was acquitted of carrying a concealed weapon (knife) because the wind accidentally caused his clothing to cover the knife).
From what my lawyer has told me, a fixed-blade carried in a bag (duffel bag, backpack) is not considered "concealed" under CA law because it is not "upon the person". I don't know about a fanny pack. It might be possible for a prosecutor to successfully argue that because the fanny pack is secured to the persons body that it is therefore "upon the person". I'd call this a
grey area, and I personally wouldn't take the chance.
As far as a vehicle, again, because the knife is not "concealed upon the person", it is perfectly legal to have a fixed-blade in your glove box, under your seat, in the center console, or anywhere else in a vehicle.
Many people carry a fixed-blade with the blade portion of the sheath in a pocket or inside the waistband. From what my lawyer has told me, as long as the knife, as it is carried, can be clearly identified as a knife, that it is very unlikely that it would be considered "concealed" in court. However, I also regard this as a
grey area. I used to carry a fixed-blade in a back-pocket sheath with the blade portion of the sheath inside my pocket and only the handle showing, but I chose to go full open-carry (sheath hanging from belt) because I didn't want to take the risk of venturing into that
grey area.
Here's my advice- If you are carrying a fixed-blade on your person, do your best to ensure that it can be clearly seen and that it can be clearly identified as a knife. I advocate full open-carry (no part of the knife handle, or the blade portion of the sheath covered by anything). This advice is based in part on the fact that I have been through the California criminal justice system, including jail, and I always recommend that people go the extra mile to avoid such experiences. I say, if you are going to carry a fixed-blade, carry it in such a way that you will have the least chance of winding up in jail.
As always, when in doubt about the law (or what you read on an internet forum), consult an actual attorney.
And just for the hell of it, since I already have it on file, here is a pick of me and my current daily carry fixed-blade, and how I carry it. Many cops have seen me carry it like this, some of them close enough to reach over and touch it, and not one of them has ever said a single word about it.