High Quality Content by WIKIPEDIA articles! The Panama Canal expansion referendum was held on October 22, 2006, when the citizens of Panama approved the Panama Canal expansion project by a wide margin. According to article 325 of the Panamanian Constitution, any proposal for the construction of a third set of locks or a sea-level Canal on the existing route that the Panama Canal Authority (ACP) proposes has to be approved by the executive branch and submitted to the National Assembly for its approval or rejection. It also has to be submitted to a national referendum no earlier than three months after its approval by the National Assembly.