Moreau began her career as a lawyer practising criminal law, constitutional law, and civil litigation. Over her career she took on cases including minority language rights and
Charter rights. In 2017, Moreau became the first woman to be appointed as the Chief Justice of the Court of Queen's Bench of Alberta. On October 26, 2023, Prime Minister
Justin Trudeau nominated Moreau to the
Supreme Court of Canada to replace
Russell Brown following his resignation on June 12, 2023, following allegations of harassment. Her appointment was confirmed on November 6, 2023, creating the first female-majority in the history of the Court. She filled one of the two seats on the bench that are traditionally allotted for judges from Western Canada. She is also a founder of the , a French-language rights organization. ==Judicial philosophy==