He was re-elected in the 2000 election in the riding of Charlesbourg—Jacques-Cartier and again in the 2004 election in the riding of Charlesbourg.
He has served as the Bloc's critic to the Solicitor General, International Trade, Indian Affairs and Northern Development, Intergovernmental Affairs, and the Privy Council.
He had co-chaired the Canada-Israel Inter-Parliamentary Friendship Group and sponsored a bill establishing a national Holocaust remembrance day.
He described himself as a "pro-Palestinian Zionist" in an op-ed piece he wrote for the Ottawa Citizen.From 2006 to 2011, Marceau worked for the Canada-Israel Committee.
Since 2011, he has worked for the Centre for Israel and Jewish Affairs as a senior advisor.