Arrested in 1924, 1933, and 1938, and sentenced to prison terms; notably, Luca was successfully defended by attorneys paid for with Red Aid funds during a 1927 trial in Cluj (where Boris Stefanov was sentenced), and was represented by Ion Gheorghe Maurer during his 1938 trial. He was serving time in Cernăuţi, having been found guilty of attempt to cross the border between the Kingdom of Romania and the Ukrainian SSR, when the Soviet Union annexed Northern Bukovina ("see Soviet occupation of Bessarabia and Northern Bukovina").