After gaining valuable experience working at the “Außenhandelsvereinigung des Deutschen Einzelhandels” (Foreign Trade Association of German Retail Trade) in Cologne/Brussels and as an in-house lawyer with the “Deutscher Direktmarketingverband” (German Direct Marketing Association), Michael founded the law firm Siegert & Keller in 1992.

His specialist fields are international data protection law and direct marketing law. He gives lectures on these subjects in Germany and abroad.