The Supreme Court of Canada doesn't often deal with humdrum disputes about a few bottles of beer. But the justices are right to have granted leave to appeal a case involving just that, because it touches on crucial matters of Canadian federalism and interprovincial trade.

The hero of the story is Gérard Comeau, a New Brunswick man who went to Quebec one day in 2012 and bought 14 cases of beer and three bottles of liquor. When he crossed back into his home province, the RCMP were waiting. He was caught and fined almost $300 for exceeding the limit on beer and liquor that can be brought in from another province.

Mr. Comeau didn't like what happened and chose to go to court, rather than pay the fine. To the surprise of a lot of people, he won his case. Judge Ronald LeBlanc wrote a thorough, 88-page decision ruling in his favour on the grounds that the British North America Act, now called the Constitution Act, 1867, had very clearly said that there should be free trade among the provinces.

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In fact, free trade was one of the main purposes for Confederation in the first place – an idea that has since been made a mockery of by interprovincial trade barriers.

Understandably, the New Brunswick government wanted to hold onto its lucrative beer and liquor monopoly. It appealed the ruling, but the New Brunswick Court of Appeal didn't see fit to prolong the dispute. The government's last chance is the Supreme Court.

The court's ruling will have huge implications. The case will be heard at the same time that the provincial governments have made some overdue progress on internal free trade in Canada.

Were the Supreme Court to sweep away barriers put up by provincial liquor monopolies, it could cascade into the elimination of all sorts of other impediments to trade in this country.

On the other hand, the court could rule that provinces are indeed within their rights to protect their jurisdictions from the complications of a free market.

All Gérard Comeau wanted was to save a few dollars on beer. Now his case is at the centre of an argument whose outcome could define this country for generations.