An Act to consolidate and amend the law relating to the Criminal Procedure.
PART VI - PROCEEDINGS IN PROSECUTIONS
CHAPTER XXX - OF PREVIOUS ACQUITTALS OR CONVICTIONS
412. Notwithstanding anything hereinbefore contained where an accused person has pleaded guilty and has been convicted by a Court of Session 399 or any Metropolitan Magistrate or Magistrate of the first class on such plea, there shall be no appeal except as to the extent or legality of the sentence.
National proceedings on admission of guilt
EDIT.