The Holy Quran tells Muslims to obey Allah and then to obey the prophet (s) and those in authority over them. So if we find something in the Holy Quran we have to follow that. But if the Holy Quran is silent then we look to the example of the Holy Prophet (s) to see if we can find any guidance in that. If there is nothing there we should turn to our leaders for guidance. But how should our leaders decided matters? The Holy Quran tells us that as well.
Our leaders should decide matters by mutual consultation among themselves and if need be with the people. We have many examples of this in the Holy Prophet’s life time where he consulted those around him and then followed the advice of the majority even when he disagreed with it.