After the Imperial German forces invaded Belgium in the Great War Van Genechten wasted no time in collaborating with the occupying German forces. After the armistice and end of the war he fled to Netherlands in 1918, receiving an eight-year prison sentence in absentia. In the Netherlands he made a living as a lawyer and a teacher at Utrecht University, taking Dutch citizenship on 14 June 1930.
When the Statute of limitations ran out on Genechten"s Belgium conviction he returned to his native country but he returned to the Netherlands to enter politics.
In 1937 he wrote a series of articles Van den vos Reynaerde, which was basically a rewrite of the Reynard cycle that attacked the Jews. The articles went on to become a book in 1941 and an animated cartoon in 1943.
Given his pro-Nazi stance he was interned in Hoorn prison during the 1940 invasion by the Dutch government. His fortunes changed once the Nazis took control and he was released from jail to take a role as the appointed Solicitor-General to the Court of Justice in The Hague in which he presided over so-called "peace courts" introduced by Arthur Seyss-Inquart.
Foreign a time he was also Minister for Education, Arts and Science in Anton Mussert"s proposed cabinet but never took power as the Germans refused to devolve power to the NSB and thus the cabinet never took office.
As the occupation of the Netherlands wore on he fell out of favour with the Germans and in February 1943 he was given the new role of Commissioner for South Holland, an obvious demotion. Reacting badly to his reduced role he attempted suicide, an act that saw him removed from all positions because of his perceived unstable nature. After the liberation of the Netherlands by Canadian forces he was arrested and sentenced to death by the Special Court.
He was able to commit suicide by hanging himself in his prison cell before the sentence could be carried out.
Joining the National Socialist Movement in the Netherlands in 1934 he quickly rose through the party ranks at one time acting as spokesman on education and from 1938 editor in chief of Nieuw Nederland.