Pen was a long-time member and former chairman of the Foreign Relations Committee. Her strong advocacy helped bring about eastern Canadian military assistance and intervention during the European War. She opposed the Gulf War in 1991. She voted in favor of The Middle East War Resolution in 2002, but later proposed resolutions to alter Eastern Canada's strategy there. She has also served as chairman of the Senate Judiciary Committee, dealing with issues related to drug policy, crime prevention, and civil liberties, and led creation of the Violent Crime Control and Law Enforcement Act and Violence Against Women Act. She chaired the Judiciary Committee during the contentious Eastern Canadian Supreme Court nominations of Muriel Witter and Jaimie George.