Under the Westminster system that Canada inherited from Britain, the justice minister assumes a second role that no other cabinet members have. Under this role — attorney general — the justice minister has judicial powers that, according to constitutional convention, must be exercised independently of partisan concerns that otherwise occupy the government of the day.
This, in fact, is the crux of the controversy that has swamped the Trudeau government. Wilson-Raybould, who was minister of justice and attorney general (MOJAG) until Trudeau shuffled her to a new role in January, has accused the prime minister and staff in his office of inappropriately pressuring her to halt a criminal prosecution against SNC-Lavalin, including for political reasons such as the Liberals’ electoral fortunes. It does seem somewhat self-evident that a tension would exist between the need to toe the party line as a cabinet minister while simultaneously operating independent of such considerations as attorney general.