One day, he was walking to school in San Juan with other students, and there was a car with four FBI agents at the corner of his house. He handed his books to the other students to take them to the place where he was living. The men arrested him and charged him with refusing the U.S. draft. The U.S. Federal Court in Puerto Rico sentenced him to two years and one day and he was sent to a prison in Tallahassee, Florida, where he remained from 1949 to 1951. During his stay in prison he confronted a prison guard because of the racist segregation inside prison walls. Under Jim Crow legislation at the time, the prison dormitories were segregated. In the 1950s, the United States entered the Korean War. Believing that he was to be drafted by the US Military and that he would once again face a prison term for refusing, Cancel Miranda followed the advice of his wife and his sister Zoraida and went into a self exile in Cuba. Cancel Miranda arrived in the city of Miranda using a different identity, Robert Rodríguez. Cuba at that time was governed by Carlos Prío Socarrás. He moved to Havana where, with the help of Albizu Campos' son, Pedro Albizu Meneses, he found a job with the Public Works Department. After a while, he went to work for the Raymond Concrete Pipe Co. which was building the Línea Street Tunnel, which connects the two banks of the Almendares River. On October 30, 1950, a Nationalist Party uprising occurred in Puerto Rico. The uprising was a call for independence against the United States Government's rule of Puerto Rico. It was also a protest against the approval of the creation of the political status the "Free Associated State of Puerto Rico" or how it is legally known, the "Commonwealth of Puerto Rico" ("Estado Libre Asociado") for Puerto Rico which was considered a colonial farce. Numerous Nationalists were arrested, among Cancel Miranda's father. In 1951, he published an article in a Havana paper to commemorate the first anniversary of that uprising. The United States embassy learned about it and demanded that the Prío Socarrás government turn him over along with another Puerto Rican, Reynaldo Trilla, but the Cuban authorities ignored them. Aracelio Azcuy, a politician of the Civil Damages Office and supporter of Prío Socarrás, used to ask Cancel Miranda to campaign for him, to write his speeches.