V.C. Section 21754 - Passing on the Right
A lot of people in this thread seem to assume we are talking about 2 lane undivided highways.
When we are talking about "passing", it generally means pulling into the oncoming lane of traffic on a 2 lane undivided highway.
Impeding traffic, same thing.
On a multi-lane divided
freeway, it is not illegal to pass another vehicle in an actual lane on the right side (at least not in CA), and you can not impede traffic, because there are plenty of other lanes for people to use.
Here in the city there are no 2 lane undivided highways. Even major streets have 4 lanes (2 in each direction)