What it's really all about: governments cannot tear up negotiated agreements
Here's what brought about this decision:
When the BC Liberals gained power in a massive, landslide victory over the NDP, they decided to arbitrarily, unilaterally tear-up a legally binding collective bargaining agreement with hospital workers in the province. This was unprecedented in BC and Canadian history.
The legal case was brought by the affected health care workers because they believed that they had a legally binding agreement in place.
The BC Liberal government of Gordon Campbell believed that it had the right to declare such an agreement null and void, so with no warning or debate they tore up the deal and gave hospital contracts to third parties.
The Supreme Court of Canada has now corrected the BC Liberal government, and by way of their ruling clarified that no government in Canada can repudiate such collective bargaining contracts unilaterally and arbitrarily.