In Canada, the criminal law is federal and uniform across the country, so there is no variation in the firemarms laws example given in the OP.
However, in other areas, the provinces have sole jurisdiction and there can be considerable variation. The clearest example is that in Quebec, the civil law is based on French/Roman civil law, while in the other provinces and territories, the civil law is based on English common law.
Another example is language - there is considerable variation in official languages. New Brunswick is the only officially bilingual province. Quebec’s official language is French, but it is constitutionally required to provide certain services in both languages. Manitoba’s official language is English, but it is constitutionally required to provide certain services in both languages. Other provinces, such as Ontario and Saskatchewan, are not under any constitutional obligation to provide any services in both languages, but do so to varying degrees.