I don't know what the exact count is, but it's remarkable how infrequently the court has had to engage with the POGG power. A few from the modern era that are most relevant to thinking about its scope. There was the anti-inflation reference from 1976, which focused primarily on the emergency branch of the POGG power. The Crown Zellerbach decision from the Supreme Court of Canada in 1988 was of huge significance because the court, by a narrow majority in that case, assigned the subject matter of marine pollution to the “national concern” branch of the POGG power. The test set out in that case is still the guiding one. It was the one that I recounted earlier.
There have been others that have discussed the power, but not upheld federal legislation pursuant to it. Perhaps the most important one to be aware of is the Hydro-Québec decision, which was released around the same time, wherein the Supreme Court of Canada said the toxic substances provisions of the Canadian Environmental Protection Act could be upheld under the criminal law power, but the court was very hesitant to even think about upholding them under the POGG “national concern” power, given the concerns that we have about the depth of the impact on provincial jurisdiction.