opening door into traffic accident

Vehicle Code, Chapter 37, Section 3705 has wording very similar to California's, and IMHO aligned with plain old good sense:

Of course, lawyers can dine out quite well over the definition of "reasonable" in this or any other issue, though if it happened just as you describe (no complicating factors such as your driving abnormally and avoidably close to parked cars, or under poor seeing conditions without lights on, or distracted...), well, my personal opinion would be, "Bet he looks before he opens his door next time!"

Depending on what problem you are trying to solve (cops decided you were partly at fault and ticketed you too? defending yourself against the other guy's insurance company? trying to get either his insurance or yours to fix your car? pick one or more) you might find that a consultation with a lawyer experienced in traffic affairs could be a few twenties well spent, even if you don't actually engage him or her to represent you in any further action.

Good thing he merely opened the door and didn't jump out of the car too! (Also a good thing you were in a car rather than on a bicycle or motorcycle -- this is referred to as "winning the door prize").

--Joe