Law is a set of rules made by authority that citizens must obey, or face punishment. It can also be used to describe a group of laws, such as all the rules of a nation.
The study of law involves a wide range of issues, from the very broad, such as the nature of government, to the very specific, such as the relationship between federal and state laws in the United States. Law is the basis for politics, economics, history and society, and shapes all of these in various ways.
One school of thought in law argues that it is best understood as an instrument for accomplishing four primary goals: establishing standards, governing societies, resolving disputes and protecting liberties and rights. The way these goals are achieved, however, varies from country to country. Most laws, for instance, reflect a balance of power between the people and the political elites who make them. In the majority of modern nations, citizens have some control over their political leaders, through democracy.
The law is based on many different traditions. Some, like the law of the land, are centuries old. Others, such as the common law, grew out of the English legal system during the 18th century. Some nations, such as Japan, adapted elements of the British legal tradition. Still other, such as India, adapted Hindu and Islamic traditions. In the United States, the common law, along with constitutional and treaty provisions, largely focuses on areas that were expressly granted to the federal government by the Constitution: immigration and nationality, military matters, money, international trade, railroads, intellectual property (specifically patents and trademarks) and mail.