21.4. The powers conferred by this Act on a judge of the Court of the Sessions of the Peace shall be exercised by a judge of the Youth Court in cases relating to a person under 18 years of age. They may be exercised by a judge of the Provincial Court or by a justice of the peace appointed under section 186 of the Courts of Justice Act (chapter T-16), if no judge of the Court of the Sessions of the Peace or the Youth Court is available in the judicial district.