This chapter discusses how Canadian constitutional issues come before the courts. Its primary focus is on litigation arising under the Charter of Rights and Freedoms. Since the entrenchment of the Canadian Charter in 1982, traditional legal process doctrines, such as standing, intervention, costs, and reference opinions have seen significant expansion. Though initially cautious, Canadian courts have recognized that the ability to initiate constitutional claims is integral to the principle of legality. The mechanisms by which constitutional issues are judicially reviewed, and decisions regarding who may participate and how such litigation may be supported, are crucial determinants of substantive constitutionalism in Canada.