Horayot 7 - Mistake of the High Priest
If the High Priest, anointed for service with Temple oil, is himself a Sage and ruled that something normally forbidden on the pain of excision is allowed, and then, without realizing his mistake, performed the act, he brings a special sacrifice, the "Anointed Kohen's bull." If he knowingly ruled incorrectly or knowingly performed the forbidden act, he does not bring this sacrifice. His law is thus similar to the court's ruling that it makes for the community.
If he ruled incorrectly together with the court and performed the act together with the congregation, he does not bring his special sacrifice but is atoned for by the communal "sacrifice of forgetfulness" bull. Just as the court is only liable if it negates a part of a commandment, but not the whole commandment, so too the High Priest.
Art: John Byam Liston Shaw - And Who Knoweth Whether He Shall Be A Wise Man Or A Fool