After completing his referendary and final Staatsexamen Lehr decided to pursue a career in local administration because of the personal autonomy and variety such a position offered.

He began working as an assessor for the municipality of Düsseldorf in 1913[1] In December 1914 at the age of 31, Lehr was elected department head of the police, in which role he was responsible for controlling the press, surveying food supply, counterespionage, and combating radical forces.

[3] During a board meeting on 12 April 1933, only weeks after the Enabling Act (‘’Ermächtigungsgesetz’’), ‘’Oberbürgmeister’’ Lehr was arrested on charges of bribery and personal gain.

In 1935, Lehr joined a Düsseldorf resistance group consisting of multiple prominent individuals of the Weimar Era including former Union Secretary Karl Arnold and evangelical lawyer Franz Etzel.

Lehr remained active in other areas of society as well, serving as President of the ‘’Schutzgemeinschaft Deutscher Wald’’, an environmental association, from 1947 until 1956 and acting as the head of the ‘’Marburger Universitätsbund’’ from 1952 until his death.