Part of it is different schools of legal thought. In America there is a significant legal tradition of "textualists' who try to read US constitutional documents literally and in a narrow focus.
Canada, for various cultural and political reasons both pre and post Charter of Rights and Freedoms has a much stronger tradition of 'living tree' constitutionalism that sees constitutional documents as able to grow and change as the values of a society change over time.
Canada, for various cultural and political reasons both pre and post Charter of Rights and Freedoms has a much stronger tradition of 'living tree' constitutionalism that sees constitutional documents as able to grow and change as the values of a society change over time.