Rabbinic enactments are all supported by the biblical law of "Lo tasur," forbidding straying from after their words: Berachot 19b
The rabbis strengthening their enactments beyond the strength of biblical law, to protect the enactment [עשו חיזוק לדבריהם יותר משל תורה]: Eruvin 3a, 68b, 77a, 85b; Rosh HaShanah 19a; Ketuvot 56a-b; Bava Metzia 55b
The rabbis strengthen their enactments specifically for cases that are common: Ketuvot 56a-b
The rabbis do not strengthen their enactments in cases where the halachic problem they are concerned about may not be an issue: Ketuvot 56b
One who changes any element of the Rabbinically instituted format of a Bill of Divorce: Gittin 5b
Collecting the Ketubah from the poorest quality of grain, as a rabbinic enactment: Ketuvot 10a
Refusing an enactment which was established for one's benefit: Bava Kama 8b
Refusing an enactment because it does not help: Bava Metzia 49b
From the time when the Rabbinic Prohibition against owning chametz sets in, chametz no longer belongs to its owner, except for liability for the prohibition against owning the chametz: Pesachim 6b-7a, 21b
One is not considered to be the owner of a pit dug in public property, except under the Rabbinic designation for liability: Pesachim 6b-7a
Creating an edict which will require extraordinary expenditure of money or physical effort: Pesachim 10b
The rabbis may decide who is credible to testify regarding rabbinic institutions: Ketuvot 10a, 55b
Divine Punishment for ignoring Rabbinic Law: Berachot 4b, Shabbat 110a
The purpose of a rabbinic decree, which erects a fence around Torah, is to make a rule which will, itself, be treated leniently: Eruvin 58b-59a
