It is a business decision, but government rules and regulations impact the cost/benefit analysis of that business decision.

Two obvious things that jump to mind are:
- More stringent environmental regulation
- Carbon taxation

Were these the only considerations?  Certainly not.  They probably weren't even the biggest considerations (the approval of Keystone XL was probably the biggest recent change), but they would factor into the overall cost/benefit analysis than companies go through when making business decisions.