Is the one who abandons ruling by what Allah has revealed considered a disbeliever if he makes judgment in general according to man-made laws, and is there a difference between him and one who judges by the Sharia but then rules in some cases contrary to the Sharia out of personal desire or bribery?

A distinction must be made between someone who replaces Allah's rule with human rule—this is disbelief that expels one from the faith—and a disobedient Muslim who follows his desires while acknowledging his wrongdoing—this person does not disbelieve. However, whoever believes that ruling by laws is like ruling by Sharia (definition) and deems it permissible, even in a single case, commits an act of disbelief.