In the memo, OLC lawyers write that the president, who has not been asked or subpoenaed to testify, must be allowed to have a representative present in depositions to be able to protect privileged information from disclosure.
The House Intelligence Committee, which is leading the ongoing investigation, has so far only allowed witnesses to appear for depositions with personal counsel.
OLC attorneys cite a DC Circuit court opinion comparing an impeachment inquiry with a grand jury investigation in a criminal probe, setting up the need to meet a high threshold to overcome the protections of the privilege.
The administration's new legal memo is untested in court.
The memo was released Monday and written on Nov. 1, the day after the House approved the rules of an impeachment inquiry in a full floor vote.