Upon completing military service as an officer in the United States Army, Fr. Araujo served as a trial attorney and attorney advisor in the Solicitor's Office of the United States Department of the Interior (1974-1979). In 1979 he joined the Law Department of The Standard Oil Company (Ohio) and served in a variety of capacities until 1985. After corporate service, he joined the general corporate department of a New England law firm and remained there until entering the Society of Jesus in 1986. Since 1997, he has served as an advisor to the Holy See providing counsel on issues dealing with public international law. He was a member of the law faculty at Gonzaga University from 1994-2005 and became the Robert Bellarmine, S.J. University Professor in American and Public International law; then he was Ordinary Professor, the Pontifical Gregorian University, 2005-2008. He has been a visiting Professor at Georgetown University Law Center; St. Louis University School of Law; and Boston College School of Law. In the academic year 2000-2001, he was the Stein Fellow at Fordham University Law School. During his graduate legal studies in New York, he was the Chamberlain Fellow at Columbia University School of Law.

He was appointed as the inaugural holder of the John Courtney Murray, S.J. University Professorship at Loyola University in July of 2009.

He is a contributor to the Mirror of Justice, a web log dedicated to the development of Catholic Legal Theory, http://www.mirrorofjustice.blogs.com.

He has authored numerous law review articles on topics that include jurisprudence, public international law, Constitutional law, and Catholic legal theory. He has coauthored a series of books on papal diplomacy and international organizations with the late Fr. John A. Lucal, S.J. In addition, he has contributed chapters to a number of volumes addressing topics in jurisprudence and public international law.