Why are gas prices in California way higher than the rest of the country?

California’s gas prices are always higher than the national average due to state taxes and regulations, but currently California’s gas is almost $3 more than the national average, which is the largest gap in history.

All I can get out of news articles as to why it is so much higher than it should be is “we don’t know” and “it’s a mystery” and caution against blaming oil companies. After all, their pricing strategies are “shrouded in secrecy”, according to the San Jose Mercury. So what is the actual reason? I know we have a lot of California residents here, so what is your opinion on this?