British North America Act, 1867, S. 129
129. Except as otherwise provided by this Act, all Laws in force in Canada, Nova Scotia, or New Brunswick at the Union, and all Courts of Civil and Criminal Jurisdiction, and all legal Commissions, Powers, and Authorities, and all Officers, Judicial, Administrative, and Ministerial, existing therein at the Union, shall continue in Ontario, Quebec, Nova Scotia, and New Brunswick respectively, as if the Union had not been made; subject nevertheless (except with respect to such as are enacted by or exist under Acts of the Parliament. of Great Britain or of the Parliament of the United Kingdom of Great Britain and Ireland,) to be repealed, abolished, or altered by the Parliament of Canada, or by the Legislature of the respective Province, according to the Authority of the Parliament or of that Legislature under this Act.
[Note: The restriction against altering or repealing laws enacted by or existing under statutes of the United Kingdom was removed by the Statute of Westminster, 1931 (No. 27 infra), except in respect of certain constitutional documents. See also Part V of the Constitution Act, 1982 (No. 44 infra).]