Treaty of Meerssen
Reginar was lay abbot of important abbeys stretching from the Meuse () to the Moselle through the Ardennes, Saint-Servais in Maastricht, Echternach, Stavelot-Malmedy, and Saint-Maximin in Trier. All these abbeys lay on or near the boundary negotiated between the Eastern and Western Frankish kingdoms in the Treaty of Meerssen in 870, during a period when the Western Kingdom controlled much of Lotharingia. In Echternach, he was referred to as "Rainerus iunior" because the lay abbot before him, a probable relative, had the same name.