Ruete studied law in Marburg, Cologne, Berlin and Gießen and obtained his doctorate in 1984 at the University of Gießen with a thesis on copyright, intellectual property and British collecting societies.
He joined the European Commission in 1986. He held various administrative positions before taking over the Directorate-General for Energy and Transport (DG TREN) in 2006 . 
From 2014 to 2017, he was Director General of the European Commission’s Directorate-General for Migration and Home Affairs. 
From March 2018, he was a special adviser in the Secretariat-General of the European Commission in charge of strategic issues related to the Energy Union, the Security Union, subsidiarity and proportionality. 
As of 1 January 2019, he was appointed by the European Commission’s Directorate-General for Mobility and Transport as one of the eleven European Transport Coordinators for the European Rail Traffic Management System (ERTMS) , in which he succeeds Belgian Karel Vinck for four years.