According to the Soviet-style Cuban constitution of 1976, the National Assembly of People's Power, and its Council of State when the body is not in session, has supreme authority in the Cuban system. Since the National Assembly meets only twice a year for a few days each time, the 31-member Council of State wields power. The Council of Ministers, through its 9-member executive committee, handles the administration of the economy, which is state-controlled except for a tiny and shriveling open-market sector. Fidel Castro is President of the Council of State and Council of Ministers and his brother Raul serves as First Vice President of both bodies as well as Minister of Defense.

Although the constitution theoretically provides for independent courts, it explicitly subordinates them to the National Assembly and to the Council of State. The People's Supreme Court is the highest judicial body. Due process is routinely denied to Cuban citizens, particularly in cases involving political offenses. The constitution states that all legally recognized civil liberties can be denied to anyone who opposes the "decision of the Cuban people to build socialism." Citizens can be and are jailed for terms of 3 years or more for simply criticizing the communist system or Fidel Castro.

The Communist Party is constitutionally recognized as Cuba's only legal political party. The party monopolizes all government positions, including judicial offices. Though not a formal requirement, party membership is a de facto prerequisite for high-level official positions and professional advancement in most areas, although a tiny number of non-party members have on extremely rare occasions been permitted by the controlling Communist authorities to serve in the National Assembly. The Communist Party or one of its front organizations approves candidates for any elected office. Citizens do not have the right to change their government. In March 2003, the government carried out one of the most brutal crackdowns on peaceful opposition in the history of Cuba when it arrested 75 human rights activists, independent journalists and opposition figures on various charges, including aiding a foreign power and violating national security laws. Authorities subjected the detainees to summary trials and sentenced them to prison terms ranging from 6 to 28 years. Amnesty International identified all 75 as "prisoners of conscience." The European Union (EU) condemned their arrests and in June 2003, it announced its decision to implement the following actions: limit bilateral high-level governmental visits, reduce the profile of member states' participation in cultural events, reduce economic assistance and invite Cuban dissidents to national-day celebrations. See also the Department's Country Report on Human Rights Practices for Cuba.

Although the constitution allows legislative proposals backed by at least 10,000 citizens to be submitted directly to the National Assembly, in 2002 the government rejected a petition known as the Varela Project, supporters of which submitted 11,000 signatures calling for a national referendum on political and economic reforms. Many of the 75 activists arrested in March 2003 participated in the Varela Project. In October 2003, Project Varela organizers submitted a second petition to the National Assembly with an additional 14,000 signatures. Since April 2004, some prisoners of conscience have been released, seven of whom were in the group of 75; all suffered from moderate to severe medical conditions and many of them continue to be harassed by state security even after their release from prison. Moreover, in response to a planned protest by activists at the French Embassy in Havana in late July 2005, Cuban security forces detained 33 opposition members, three of whom had been released on medical grounds. At least 16 other activists were either arrested or sentenced to prison since 2004 for opposing the Cuban Government. There has also been a resurgence of harassment of various activist groups, most notably the "Damas en Blanca," a group of wives of political prisoners.