Shalom,
What is the actual parameters of the Mitzvah of Lo Tasur?
As per the reading of the Rambam it seems that every time that you fail to perform or that you violate a Rabbinic Mitzvah you are actually violating the Torah as well? Is this the correct understanding or it’s more about a general acceptance of the Rabbinic authority?
Lo Tasur — Clarification According to the Rambam and the Lechem Mishneh
The Rambam’s language in Hilchot Mamrim can easily be misunderstood if read in isolation. One might mistakenly conclude that every violation of a Rabbinic enactment automatically constitutes a violation of a Torah prohibition (Lo Tasur). That reading, however, cannot be correct, and the Rambam himself does not mean it that way.
This point is made explicitly and clearly by the Lechem Mishneh on that very Rambam.
The Lechem Mishneh explains that Lo Tasur is not violated by the mere failure to observe a Rabbinic decree. Rather, the Torah prohibition applies only when one rejects the authority of the Sanhedrin that issued the ruling. The Rabbinic law remains Rabbinic in its halachic status; the Torah command is directed at rebellion against the judicial authority, not at the intrinsic content of the enactment.
In other words, violating a Rabbinic law does not automatically turn the act into a Torah violation. If it did, there would be no meaningful distinction between Torah law and Rabbinic law, and the entire halachic system of levels—de’oraita versus derabbanan, safek de’oraita lechumra versus safek derabbanan lekula—would collapse. Since those distinctions are fundamental and universally accepted, it is clear that Lo Tasur cannot function in that way.
This is also why the Rambam places this discussion specifically in Hilchot Mamrim. The Torah is addressing a case of defiance, not ordinary non-compliance. The classic case is a qualified scholar who argued a matter before the Sanhedrin, heard their final ruling, and then returned to rule or act against it because he rejected their authority. He is known as a Zaken Mamre. That is Mamrim. That is the context of Lo Tasur.
An ordinary violation of a Rabbinic enactment—whether out of weakness, desire, negligence, or even disagreement—remains just that: a violation of Rabbinic law. Lo Tasur is violated only when the act expresses a conscious refusal to accept the authority of the Sanhedrin as the final decisional body.
This understanding, articulated clearly by the Lechem Mishneh, preserves both the Rambam’s intent and the entire structure of halacha. It explains why Rabbinic laws remain Rabbinic, why doubts (Safek) in Rabbinic law are treated leniently, and why Judaism has always recognized multiple levels of obligation rather than collapsing everything into a single, all-or-nothing category.