The study of ways to amend a constitution was never an easy question, overall considering the different political traditions and constitutional choices. Besides the clear formal limits to restrain a constitutional amendment, there are othe possibilities, that differs by nature and constitutional stability, such as: temporal limits, material limits and circunstantial limits. Those options changes in every constitutional choices and time to time. Nevertheless, the doutrinary approach reveals some important accomplishment in protecting an essential forms of every constitution. Those implicit limits have an arreay in common, even if not writting they are the last defence against the overacting of political power (in form of parlament or presidential). This seminar examines the fortitude of those implicit limits to amend a constitutional when they are challenged. This study will offer a constitutional comprative approach.