Neven,
As I understand, accounting for assets within a business is a grey area called 'fair value' which is generally what you could sell in an orderly fashion, this is in between a fire sale price and the future profit it could generate.
Companies manage their assets and should assign a realistic fair value on a asset. This is exactly the hole banks fell into during the financial crisis when they bundled up loans into assets and assigned a 'fair value' to them of far higher than their actual value.
The oil companies count future drilling rights as assets on their balance sheets. The problem is that to hit any of our existing targets the majority of assets are going to be left in the ground.
So if ABC Oil company has tar sands which it has discovered and/or bought a licence to exploit it can book the asset at 'fair value' which assumes they are to be fully exploited in the future. If a new law makes exploiting this illegal, and the fair value of these becomes zero so ABC Oil company now has to declare a 100% loss on these assets. If the remaining assets the company has exceeds their debt the company is insolvent and will go bust.
The problem with this is of course that at some point we need to mitigate for climate change, but this has not been reflected in the valuations of oil companies worldwide. 80% of known reserves (which are on the oil companies and government books) need to be left in the ground to hit the targets set under Kyoto, and the oil companies are still exploring for more. To make things worse, as oil increases in value due to Peak Oil the assets increase in value, and we get an even bigger bubble.
When the s*** finally starts hitting the fan mitigation is going to become more of a priority, laws will be passed and the oil companies assets will become worthless. As with the financial crash of '08 when assets become worthless bad things happen.
See
http://www.carbontracker.org/carbonbubble for more info.