Don't know about CA laws.
I am familer with the V-due, it was always questionable whether it would be legal here, it origionally was supposed to have a FI system that would have allowed it to pass emmisions, but they never got that to work very well. Most if not all V-Due's had carbs retrofitted. Roehr did some work on DI two stroke motorcycles and seems to understand the process much better than Bimota did, but in the end decided that it wouldn't be a wise business move. He is now building a 950cc 4-stroke twin that looks quite promissing, but less fun than the RV500:)
If you ever want to sell that V-due please contact me, I'd be very very interested.
The EPA typicaly does not regulate only the emmisions output, but also the technical charcteristics of most everything under its ever-expanding domain. This means, that even if you could make a clean 2-stroke, it would not necessarily be allowed in the US.
still, all the above does not preclude converting an off-road only 2stroke for street use. This will vary by state. I know of street legal KDX's and CR250R's here in va:)