What is Equal Authenticity Rule?

Legal Definition
The equal authenticity rule is a rule of judicial interpretation developed by Canadian courts as a way of interpreting laws which are written in two parallel texts in English and French. The constitution of Canada requires that both versions of each Canadian law be treated as equally authoritative, which can result in problems when the English and French versions do not say exactly the same thing. The equal authenticity rule is derived from section 133 of the Constitution Act, 1867, which states, inter alia, "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].”
-- Wikipedia