The role of the High Court varies depending on the country. Here are the roles of the High Court in Australia, the United States, and the United Kingdom:

Australia

• The High Court is the highest court in the Australian judicial system.
• Its functions are to interpret and apply the law of Australia, decide cases of special federal significance including challenges to the constitutional validity of laws, and hear appeals, by special leave, from Federal, State and Territory courts.

United States

• The Supreme Court of the United States is the highest tribunal in the nation for all cases and controversies arising under the Constitution or the laws of the United States.
• Its role is to ensure the American people the promise of equal justice under law and, thereby, also functions as guardian and interpreter of the Constitution.
• The Supreme Court decides the constitutionality of federal laws and resolves other disputes about federal laws.

United Kingdom

• The High Court of Justice is one of the senior courts of England and Wales.
• It deals at first instance with all high-value and high-importance civil law (non-criminal) cases; it also has a supervisory jurisdiction over all courts in England and Wales.
• The High Court consists of three divisions: the Kings Bench Division, the Chancery Division, and the Family Division.
• Most High Court proceedings are heard by a single judge, but certain kinds of proceedings, especially in the Kings Bench Division, are assigned to a divisional court—a bench of two or more judges.

In summary, the role of the High Court is to interpret and apply the law, decide cases of special federal significance, and hear appeals from lower courts. The High Court is the highest court in the judicial system of the country it serves.