Various mechanisms apply. From an administrative standpoint, the minister can adjust the passing grade. New regulations can be made. Legislative changes can be brought in if the legislation is no longer deemed adequate. Various options are possible, depending on what you are trying to achieve.
Evidence of meeting #44 for Citizenship and Immigration in the 39th Parliament, 2nd Session. (The original version is on Parliament’s site, as are the minutes.) The winning word was instructions.
A recording is available from Parliament.