In 1989, at the beginning of his administration, President George H. W. Bush appointed Barr to the U.S. Department of Justice as Assistant Attorney General for the Office of Legal Counsel (OLC), an office which functions as the legal advisor for the President and executive agencies. Barr was known as a strong defender of presidential power. He wrote an advisory opinion justifying the U.S. invasion of Panama and arrest of Manuel Noriega. He wrote legal justifications for the practice of rendition, so that the FBI could enter onto foreign soil without the consent of the host government to apprehend fugitives wanted by the United States government for terrorism or drug-trafficking. Barr declined a congressional request for the full 1989 opinion, but instead provided a document that "summarizes the principal conclusions". Congress subpoenaed the opinion, and its public release after Barr's departure from the Justice Department showed he had omitted significant findings in the opinion from his summary document.