In the Vienneau case, which was brought before the Federal Court, the complainant cited exactly this issue in his complaint to the Office of the Information Commissioner. His ATI request was denied and he was simply told that subsection 15(1) had been invoked. He was not given any further information and was not told which paragraph of the subsection had been invoked. He complained about that. The Federal Court referred the case to the court of first instance. Citizens are entitled to file complaints with the commissioner. The commissioner then carries out an inquiry and seeks further clarification. If the case ends up before the courts, the supplementary information is revealed through the judicial process.
On May 31st, 2007. See this statement in context.