He wrote his dissertation Der Geisel im modernen Völkerrecht (The hostage in modern international law) in 1932 at the University of Erlangen.
He became a member of the Nazi Party in 1940 and volunteered for the Kriegsmarine to avoid being questioned about his Jewish ancestors.
In 1947, he practiced law in the Nürnberg High Command Trial, defending General Rudolf Lehmann.
In 1957, he began working in Bonn on trade agreements with Malaysia, Iran, Pakistan and several African countries.
In 1965, von Keller was awarded the Großes Verdienstkreuz mit Stern (Knight Commander).