Horayos 1:2-3

Horayos 1:2

If the court made a ruling, realized they had erred, and retracted that ruling, whether this happened before they brought their atonement offering or had not yet done so, if someone acted based on their decision, Rabbi Shimon says he is exempt. Rabbi Eliezer declares it a case of doubt as follows: if the individual remained at home, he is liable (because he was in a position to confirm the ruling) but if he went abroad, he is exempt (because he was not in a position to receive the updated information). Rabbi Akiva said that he is inclined to agree that one who went overseas should be exempt rather than liable. Ben Azzai asks why he should be different from one who stayed home. Rabbi Akiva responded because the one who stayed home could have heard of the retraction but the traveler could not. (Rabbi Akiva and Ben Azzai actually differ regarding one who is about to leave on such a journey and is preoccupied with his preparations.)

Horayos 1:3

If the court made a ruling that invalidated the entire corpus of a mitzvah, such as by saying that there’s no family purity in the Torah, no Shabbos in the Torah, or no idolatry in the Torah, they are exempt. (Such a ruling is so clearly ineffective that one who relies upon it is actually acting of his own volition.) If the court invalidated part of a body of laws and upheld the other part, then they are liable. Examples of such a thing would include ruling that there is such a thing as family purity but that a man is exempt for having relations with his wife when she is observing her status from day to day; there is such a thing as Shabbos but a person is exempt for carrying from a private domain to a public domain; idolatry is prohibited but one who merely bowed to an idol is exempt. The court is liable for rulings such as these as per Leviticus 4:13, “And something be concealed” – something from a body of laws is concealed from them but not the entirety of it.