My experience with bringing out of state vehicles in to Ca is as follows:
You will have to take the vehicle to a CA DMV to do a 'VIN verification'.
As long as your vehicles have the emissions stickers that the DMV is looking for, you will be ok.
Not sure though how it works with EU spec vehicles.
Don't take my word for it though, I'd recommend you visit the DMV website for further information:
Be warned though, CA has stringent emissions laws when compared to just about any other state...