After his release from prison, Brown became a longshore worker and joined the International Longshoremen's Association, which was the predecessor of the ILWU on the west coast of the United States, as part of CPUSA's shift away from its strategy of dual unionism.
[1][2][3][6] In 1938, after being denied a passport by the US government, Brown stowed away on a ship to France and traveled to Spain to join the Abraham Lincoln Brigade.
[1] Advised by CPUSA leadership, Brown spent the first half of the 1950's in hiding due to repression against communists in the United States.
[2][3] In the late 1950's, Brown was elected to the executive board of the International Longshore and Warehouse Union, Local 10 (San Francisco).
In 1961, he was arrested and charged with violating section 504 of the Landrum-Griffin Act, which barred communists from holding leadership positions in labor unions.
He remained involved in left-wing causes, including supporting the Sandinistas in Nicaragua and opposing the dictatorship of Augusto Pinochet in Chile.