The latter. The atmosphere is generally viewed as a convenient place to dump whatever with no consequences. Like the ocean!

No consequences at all, nosiree.

There are laws to penalize leaks if the leak is caused by misconduct like not following safety protocol or not built with safety measure. But the penalty is so lightweight corps just ignore. There are too many drilling leaks every day, so what? $250,000 fine? Fuck that. Easy money and it is the practice of energy company to sub-contract the drilling so fault will never end up on them. Sub-contractors sub-contract and more sub-contract. Yeah, a merge sort, but penalty never bubble up. Also, there aren't enough human resource available to do inspection.

Yes, CA law states that SoCalGas has to account for the leak by cutting emissions in other places. I think even before the government mandate SoCalGas said they will do compensate for the leak by cutting back in other emissions. So the net effect should be zero after some years.

In practice the entity which actually spills the toxic waste conveniently has no assets to recover. See many many historical cases of US vs. Cult of The Invisible Hand, Incorporated cases since the 80s. You need federal-government-scale investigation and prosecution resources to go after the money behind the shell companies. Also it's quite possible for anyone to cause an ecological catastrophe far beyond their ability to recompense.

There is a dead simple solution to this which we've known about forever. Require companies that drill for oil to carry adequate insurance.

The paper on the economics of this is The Problem of Social Cost by Ronald Coase. It's dense but readable, and a masterpiece of economic reasoning.