I don't know about where you live, but here (Atlanta) the blade limit is 3", regardless of who you are. In most of the United States, I don't think age matters much. Though some places like to give kids a hard time.
And for me, anything over than 0.2" on a warden is too thick. The thinner the better, as in the 0.14" OJs or the Bad Wardens. Specifically, the fatties, like the blue/ black G10 and black/tan G10 wardens in Vassily's pics above, are too thick. I can't remember the precise thickness, but I think they're .0.25" at least. I have one and it's cool, but simply too thick and heavy to be practical IMO. There is a huge difference in slicing ability between the thick and thin models. And the fatter ones seem to be almost twice as heavy.
Many of the wardens will need to be reprofiled to get anywhere near a standard sharpening angle (again, see Vassily's pics above). I bet he can tell you the angle. I don't bother with it myself, I simply walk across the street and have a professional do it for me. My sharpening technique sucks.