A Cherem is not proclaimed during the days between R”H and Yom Kippur. Likewise a court does not swear a defendant during these days. However to have court proceedings between two people certainly is a great Mitzvah as by doing so one removes the stolen item from the perpetrator, and when one does judgment below there is no judgment above. If however a swear must be imposed between them then the court case is to be delayed until after Yom Kippur.
 602/5; Rama 602/1
 The reason: As we do not desire to arouse the powers of judgment during this time. [ibid]
Other customs: Some are accustomed not to impose a Cherem throughout the entire month of Tishrei. [Chasam Sofer Choshen Mishpat 77]
 The reason: As we do not want to bring retribution in the world for swearing during this time. [Admur ibid; Taz 602/1] Some say this only applies to swears about past events while future events are permitted to be sworn about. Others however argue on this. [See Poskim in Piskeiy Teshuvos 602/3 footnote 11-12] It is likewise disputed if one may volunteer to swear during this time. [See ibid]
 Admur ibid; Levush 603; Taz 602/1; M”A 602/1; M”E 602/33; Ruach Chaim 602/1; M”B 602/9; Kaf Hachaim 602/16