In June 1950 Beloyannis returned to Greece in order to re-establish the Athens organization of the Communist Party of Greece (KKE) that had been declared illegal. He was arrested on December 20 1950 and was taken before a court-martial on charges of violating Compulsory Law 509/1947, which criminalized the Communist Party of Greece (KKE).He was also accused of being a traitor, transmitting information to the Soviet Union.
The Beloyannis trial started in Athens on October 19th 1951. In total, 94 people were accused. One of the three members of the court-martial was Georgios Papadopoulos who later (1967) became the leader of the military dictatorship of 1967-1974.
Beloyannis denied all accusations and stressed the patriotic nature of his actions during the anti-Nazi resistance (1941—1944), the British intervention (1944—1946) and the Greek Civil War (1946—1949). He became globally known as the "Man with the Carnation" and as such he was depicted in a famous Pablo Picasso sketch.
Despite national and international appeals for clemency, the court-martial sentenced Beloyannis and three of his fellows to death. They were taken from the prison of Kallithea early in the morning of Sunday March 30, 1952 and were executed in the Goudi camp.
Beloyannis became one of the great heroes of the Greek left. His name was given to the village of Beloiannisz built in Hungary to house the Greek political refugees who lived in exile from the end of the civil war (1949) until the fall of the Papadopoulos junta and the re-establishment of democracy in Greece (1974).