Is replacing the Sharia with man-made laws in itself an act of disbelief (kufr), or is it because it indicates a preference for man-made laws over the Sharia?

Sheikh Muhammad bin Ibrahim Al Al-Sheikh holds that ruling by man-made laws is major disbelief (kufr akbar), even if the ruler does not believe them to be superior to Allah's Sharia. He divided major disbelief into categories, making the preference of something other than the Sharia one category, and ruling by man-made law another. Thus, ruling by other than what Allah has revealed is disbelief if the ruler believes that the rule of someone other than the Messenger is better, more complete, or more comprehensive. The same applies if there are courts that rule by fabricated laws that contradict the Book and the Sunnah.