La Forest stated that the test for "colourability" is whether the law has a "legitimate public purpose" that underlies the prohibition.

La Forest rejects Hydro-Québec's argument that the Act was merely a regulatory scheme and did not constitute criminal law.

He noted that the Act "is an effective means of avoiding unnecessarily broad prohibitions and carefully targeting specific toxic substances."

The provisions of the Act are not directed at the general protection of the environment but rather targets to control dangerous and toxic substances.

Lamer then considered whether the law would fall under "national dimension" of the federal peace, order and good government power.

To apply the law must concern a "new" subject "must have a singleness, distinctiveness and indivisibility that clearly distinguishes it from matters of provincial concern and a scale of impact on provincial jurisdiction that is reconcilable with the fundamental distribution of legislative power under the Constitution" Lamer held that the definition of "toxic substances" was too broad to meet this test.