The constitution that established the Fourth Republic provided a basic charter for republican democratic government. It declares Ghana to be a unitary republic with sovereignty residing in the Ghanaian people.
Intended to prevent future coups, dictatorial government, and one-party states, it is designed to establish the concept of powersharing. The document reflects lessons learned from the abrogated constitutions of 1957, 1960, 1969, and 1979, and incorporates provisions and institutions drawn from British and American constitutional models.
One controversial provision of the Constitution indemnifies members and appointees of the Provisional National Defence Council (PNDC) from liability for any official act or omission during the years of PNDC rule. The Constitution calls for a system of checks and balances, with power shared between a president, a unicameral parliament, a council of state, and an independent judiciary.
Executive authority is established in the Office of the Presidency, together with his Council of State. The president is head of state, head of government, and commander in chief of the armed forces. He also appoints the vice president. According to the Constitution, more than half of the presidentially appointed ministers of state must be appointed from among members of Parliament.
The outcome of the December 2012 elections which declared John Dramani Mahama as President of Ghana by the Ghana Electoral Commission was challenged by Nana Akuffo Addo, Bawumia and Jake Obetsebi Lamptey at the Supreme Court of Ghana of which the Supreme Court came out with the verdict that the President, John Dramani Mahama legally won the 2012 presidential election.
Legislative functions are vested in Parliament, which consists of a unicameral 275-member body plus the Speaker. To become law, legislation must have the assent of the president, who has a qualified veto over all bills except those to which a vote of urgency is attached.
The members are elected for a four-year term in single-seat constituencies by simple majority vote. As is predicted by Duverger's law, the voting system has encouraged Ghanaian politics into a two-party system, which means that there are two dominant political parties, with extreme difficulty for anybody to achieve electoral success under the banner of any other party. Elections have been held every four years since 1992. Presidential and parliamentary elections are held alongside each other, generally on 7 December.
The structure and the power of the judiciary are independent of the two other branches of government. The Supreme Court of Ghana has broad powers of judicial review. It is authorized by the Constitution to rule on the constitutionality of any legislation or executive action at the request of any aggrieved citizen. The hierarchy of courts derives largely from British juridical forms.
The courts have jurisdiction over all civil and criminal matters. They include the Superior Courts of Judicature, established under the 1992 Constitution, and the Inferior Courts, established by Parliament. The Superior Courts are, from highest to lowest, the Supreme Court of Ghana, the Court of Appeal, the High Court of Justice, and the ten Regional Tribunals.
The Inferior Courts, since the Courts Act 2002, include the Circuit Courts, the Magistrate Courts, and special courts such as the Juvenile Courts. In 2007, Georgina Wood became the first ever female chief justice of the Ghanaian Supreme Court.