From 1921 he edited a new periodical called Mot Dag, which he published together with people he met in a study circle led by Edvard Bull.
Together with Martin Tranmæl Falk was instrumental in writing the Kristiania Proposal in early 1923,[1] which stated that the Labour Party should strive for independency from the Comintern.
[2] The Comintern did not take lightly to this, and Falk was present to discuss the issue at the 3rd Enlarged Plenum of Executive Committee of the Communist International in June 1923.
[3] In 1928 he was a part of the 6th World Congress of the Comintern in Moscow,[citation needed] but Falk and Mot Dag left the Communist Party in 1928.
[3] Around the same time Falk also lost influence in the Norwegian Students' Society, due to having embezzled money from a construction fund reserve.
After the Great Depression in 1929, Falk translated Karl Marx's Das Kapital to Norwegian, and wrote the book Hvad er marxisme?
[5] One day before the German invasion of Norway in April 1940, Falk left the country for Stockholm to undergo brain surgery.