Date: 5 Tishrei 5575
From: Rabbi Moshe Sofer
To: Rabbi Simcha Bunim Ginz (Eiger)
The question asks how the Sages' oath administered to a Sadducean Kohen Gadol regarding the Ketores service could be effective. The Chasam Sofer offers multiple solutions, most compellingly that the oath's formula designating him as an agent of Beis Din means deviation would revoke his Kohen Gadol status.
Source: Shu"t Chasam Sofer OC §176