In September 1998 he was selected by delegates at the SNP's conference as a candidate for the 1999 European Parliament elections. He was elected a Member of the European Parliament, taking a leave of absence from the University of Edinburgh. Professor MacCormick was a member of the Convention on the Future of Europe from 2002 to 2003, drafting the proposed Constitutional Treaty for the European Union. He was voted Scottish Euro MP of the Year in 2001, 2002 and 2003 at the Scottish Politician of the Year Awards, and retired from elected office in 2004 to complete his Leverhulme Research Professorship at Edinburgh.