All provinces have at one time or another experienced boom and bust. The purpose of equalization and other transfers is to round off those edges - to allow provinces to provide minimum standards of living and public services. None of that is inconsistent with Canada's core structure as a federation of states. 

The provinces and the national government are each sovereign within the respective powers assigned them under the constitution. The courts are being asked to clarify one aspect of that sovereignty. 

We know the constitution precludes the application of tariffs on goods travelling between provinces but short of that there are other powers the provinces enjoy that allow them to impose what, in effect, are non-tariff barriers. The courts will examine this issue in the context of the Constitution Act but it will be guided as much or more by precedent. And precedent in this instance is decidedly on the side of the provinces.