There is no appeal: 1/ from a sentence of the Supreme Pontiff himself or the Apostolic Signatura; 2/ from a sentence tainted by a defect of nullity, unless the appeal is joined with a complaint of nullity according to the norm of can. 1625; 3/ from a sentence which has become a res iudicata; 4/ from a decree of a judge or from an interlocutory sentence which does not have the force of a definitive sentence, unless it is joined with an appeal from a definitive sentence; 5/ from a sentence or a decree in a case where the law requires the matter to be decided as promptly as possible (expeditissime).
Source: Code of Canon Law (Vatican.va)