When does His Majesty in Council's exercise of jurisdiction become invalid?
The context provided does not mention any specific conditions under which the exercise of jurisdiction by His Majesty in Council would become invalid. It only states that nothing in the Constitution shall operate to invalidate the exercise of jurisdiction by His Majesty in Council to dispose of appeals and petitions from, or in respect of, any judgment, decree or order of any court within the territory of India in so far as the exercise of such jurisdiction is authorised by law.