Date: 1808
From: Rabbi Moshe Sofer
To: Rabbi Ephraim Zalman Margolios
Rabbi Ephraim Zalman Margolios defended his ancestor the Bechor Shor's prohibition against the common practice of selling chametz-fattened animals to non-Jews before Pesach and repurchasing them afterward. The Chasam Sofer rules there is no clear proof to prohibit, arguing that ha'arama is not universally forbidden, that the non-Jew has sufficient legal intent to acquire, and that a valid sale supplemented by hefker resolves concerns.
Source: Shu"t Chasam Sofer OC §62