Normally you can't open your car door into the middle of traffic and hit someone. There's a statute that says so. Or, if you do, you're liable.
But according to the Court of Appeal, if you're a police officer who's stopped someone for doing a "California stop" at a stop sign (i.e., a "rolling stop"), that doesn't apply any more. The police officer is allowed to open his or her door directly into traffic -- here, into a motorcycle -- and there's nothing anyone can do about it. Opening a door to get out of your vehicle and ticket someone who's already pulled over apparently counts as "immediate pursuit". Hence no liability.
I'm sure that doesn't seem at all fair to the motorcyclist here. Nor to anyone else who's injured by the negligence of someone else.
Though I'm sure it seems pretty fair to police officers. As well as to cities that employ them.
See whether it seems fair to you.
Regardless, in the meantime, watch out for police cars. Assume they're going to open their doors right into traffic.
Because they totally can.