Alright, I live overseas and where I live I have to fear the Police as much or more so than the bad guys. Corruption is rampant and if you are a Westerner and have anything that they (police) want they are going to take it if you are stopped. It seems easier through situational awareness to avoid the bad guys. The country I live in has a very draconian knife law, which makes carrying any knife illegal unless it is needed for a specific occupation or activity. It seems that fixed blades are out of the question. Everywhere you go there is security personnel searching people as they go into office buildings and even malls. So only the criminals use knives in the commission of crimes - strong arm robberies, murders, kidnappings, etc. Scary stuff! Dang, makes me wonder why I live there!!
With that said, fixed blade folding knives carried closed in the pocket from all indications are legal to carry in California. Mine is a somewhat inexpensive Gerber. Solid knife with a 2 1/2 inch blade.
What I have a question about is the "Merlin Professional Folding Knife Deployment System". It is a pretty interesting piece of equipment. It holds the blade of the knife in a partially open position with the grip being held by a plastic wing into the liner.
Is this thing legal in California? It is not a fixed blade knife and carrying it under your shirt is still a closed blade knife. There has to be some real gray area here.