There is a Mishna in Pirkei Avot that says עשו סיג לתורה, to make a fence around the Torah. This means that the Rabbis are empowered to set up laws to safeguard that Torah. Their job is to be certain that they make it one step more difficult so as not to come to violate a Mitzva.
Surprisingly, this is learned from the beginning of Parshat בשלח where Hashem felt it would demoralize the people if they were to go to war immediately after the exodus. He, therefore, took them on a circuitous route in order to "make a fence" that they not be harmed.
This is also the idea behind תקנות or decrees that the Rabbis are allowed to make. They take into account the needs of a particular society so as to keep it strong during difficult and trying times. These תקנות are meant to protect and safeguard the Jewish people.