The equal authenticity rule () is a rule of judicial interpretation developed by Canadian courts as a way of interpreting laws written in parallel French and English texts. The constitution of Canada requires that both versions of each bilingual law be treated as equally authoritative, which can result in problems when the English and French versions are incongruent. The equal authenticity rule is derived from section 133 of the Constitution Act, 1867, which states, , "The Acts of the Parliament of Canada and the Legislature of Quebec shall be printed and published in both those Languages [i.e. both English and French]." History The rule requires courts to treat "both [the English and French] versions of statutes [as] equally valid and authoritative interpretations of the law." The rule holds that both versions are equally authoritative even if the statute in question was clearly drafted in one language and translated into the other, and even if the two versions of the law are incompatible. An early version of the principle may be found a statute of the Parliament of the Province of Canada, enacted in 1857. The Act respecting the Codification of the Laws of Lower Canada relative to Civil Matters and Procedure requires that the Civil Code of Lower Canada be printed only in bilingual form, with English and French displayed on the same page: "[T]he two texts, when printed, shall stand side by side." It has been suggested that this provision of the 1857 Act is "best understood as a non-verbal legislative sign that the two texts should be interpreted dialogically." Whether or not this is an overstatement, it is certainly true that side-by-side publication was the first step towards the eventual adoption of the equal authenticity rule for interpreting bilingual statutes. The equal authenticity rule was developed by the Supreme Court of Canada in 1891, in the court’s ruling in CPR v. Robinson. This case dealt with the Civil Code of Quebec, which is enacted in both French and English. By implication, the rule also related to all laws enacted by the Parliament of Canada, as section 133 of the Constitution Act, 1867 is equally binding upon the federal Parliament and Quebec legislation. The Supreme Court of Canada first applied this rule of judicial interpretation to Acts of Parliament in 1935, in its ruling in the case of R. v. DuBois. The rule was reaffirmed as subsection 18(1) of