Here we'll talk about what type of law a Zaken (elder) has to reject in order to become a Zaken Mamre (rebellious elder). Mishnah says there's something stricter about a halacha (law) in the Torah that is explained by the chachamim (the rabbis) using the tradition, as opposed to a halacha written in the Torah where it is clear what has to happen. In other words, if something is written clearly in the Torah, a Zaken Mamre is not a Zaken Mamre if he goes against it. But if the Zaken Mamre goes against something that is an interpretation of the chachamim and for which they have a tradition, but that is vague in the words of the Torah, that's where a Zaken Mamre could develop into something problematic.
For example, for example, let's say somebody says: a chacham gets up and says, “There's no obligation to wear tefillin (phylacteries).” He wants people to violate it, and he tells everyone there's no obligation to wear tefillin. Then what we say is that there's an obvious obligation to wear tefillin. It says in the Torah, “You should bind them around your arms and put them between your eyes.” A clear obligation of tefillin. So what we would say is that people should know that the chacham was just mistaken. It wasn't going against the Torah. The obligation of tefillin is written so clearly in the Torah that people should know that. And when he says not to wear it, it's not considered a ruling that he's going against for which he should be put to death. It's probably just a mistake or a misunderstanding.
But when it comes to how many compartments there are in the tefillin, we have four. Chamesh totafot lehosif. But if he says there should really be five compartments in the tefillin, which is adding to the understanding of Chazal (the rabbis), the rabbis have a tradition that there are four compartments in the tefillin. So in that case, he's chayav. He would be obligated to be put to death. That law is not written clearly in the Torah. And therefore, he's trying to undermine the tradition of chachamim. And if we didn't know of the tradition, we would think that this Zaken is right. So for that type of deviation, he would be put to death.