Law is a set of rules that are created and are enforceable by social or governmental institutions to regulate behavior,^[1] with its precise definition a matter of longstanding debate.^[2][3][4] It has been variously described as a science^[5][6] and as the art of justice.^[7][8][9] State-enforced laws can be made by a group legislature or by a single legislator, resulting in statutes; by the executive through decrees and regulations; or established by judges through precedent, usually in common law jurisdictions. Private individuals may create legally binding contracts, including arbitration agreements that adopt alternative ways of resolving disputes to standard court litigation. The creation of laws themselves may be influenced by a constitution, written or tacit, and the rights encoded therein. The law shapes politics, economics, history and society in various ways and also serves as a mediator of relations between people.

Legal systems vary between jurisdictions, with their differences analysed in comparative law. In civil law jurisdictions, a legislature or other central body codifies and consolidates the law. In common law systems, judges may make binding case law through precedent,^[10] although on occasion this may be overturned by a higher court or the legislature.^[11] Historically, religious law has influenced secular matters and is, as of the 21st century, still in use in some religious communities.^[12][13][14] Sharia law based on Islamic principles is used as the primary legal system in several countries, including Iran and Saudi Arabia.^[15][16]

The scope of law can be divided into two domains: public law concerns government and society, including constitutional law, administrative law, and criminal law; while private law deals with legal disputes between parties in areas such as contracts, property, torts, delicts and commercial law.^[17] This distinction is stronger in civil law countries, particularly those with a separate system of administrative courts;^[18][19] by contrast, the public-private law divide is less pronounced in common law jurisdictions.^[20][21]

Law provides a source of scholarly inquiry into legal history,^[22] philosophy,^[23] economic analysis^[24] and sociology.^[25] Law also raises important and complex issues concerning equality, fairness, and justice.

Legal systems

In general, legal systems can be split between civil law and common law systems.^[76] Modern scholars argue that the significance of this distinction has progressively declined. The numerous legal transplants, typical of modern law, result in the sharing of many features traditionally considered typical of either common law or civil law.^[63][77] The third type of legal system is religious law, based on scriptures. The specific system that a country is ruled by is often determined by its history, connections with other countries, or its adherence to international standards. The sources that jurisdictions adopt as authoritatively binding are the defining features of any legal system.

Areas of law

All legal systems deal with the same basic issues, but jurisdictions categorise and identify their legal topics in different ways. A common distinction is that between “public law” (a term related closely to the state, and including constitutional, administrative and criminal law), and “private law” (which covers contract, tort and property).^[g] In civil law systems, contract and tort fall under a general law of obligations, while trusts law is dealt with under statutory regimes or international conventions. International, constitutional and administrative law, criminal law, contract, tort, property law and trusts are regarded as the “traditional core subjects”,^[h] although there are many further disciplines.

International law

United Nations Security Council in 2005International law can refer to three things: public international law, private international law or conflict of laws and the law of supranational organisations.

• Public international law concerns relationships between sovereign nations. The sources for public international law development are custom, practice and treaties between sovereign nations, such as the Geneva Conventions. Public international law can be formed by international organisations, such as the United Nations (which was established after the failure of the League of Nations to prevent World War II),^[i] the International Labour Organisation, the World Trade Organisation (WTO), or the International Monetary Fund. Public international law has a special status as law because there is no international police force, and courts (e.g. the International Court of Justice as the primary UN judicial organ) lack the capacity to penalise disobedience. The prevailing manner of enforcing international law is still essentially “self help”; that is the reaction by states to alleged breaches of international obligations by other states.^{[163][1][164]} However, a few bodies, such as the WTO, have effective systems of binding arbitration and dispute resolution backed up by trade sanctions.^[165]
• Conflict of laws, or private international law in civil law countries, concerns which jurisdiction a legal dispute between private parties should be heard in and which jurisdiction’s law should be applied. Today, businesses are increasingly capable of shifting capital and labour supply chains across borders, as well as trading with overseas businesses, making the question of which country has jurisdiction even more pressing. Increasing numbers of businesses opt for commercial arbitration under the New York Convention 1958.^[166]
• European Union law is the first and so far the only example of a supranational law, i.e. an internationally accepted legal system, other than the United Nations and the World Trade Organization. Given the trend of increasing global economic integration, many regional agreements—especially the African Union—seek to follow a similar model.^[167][168] In the EU, sovereign nations have gathered their authority in a system of courts and the European Parliament. These institutions are allowed the ability to enforce legal norms both against or for member states and citizens in a manner which is not possible through public international law.^[169] As the European Court of Justice noted in its 1963 Van Gend en Loos decision, European Union law constitutes “a new legal order of international law” for the mutual social and economic benefit of the member states.^{[170][171][172]}

Constitutional and administrative law

The French Declaration of the Rights of Man and of the CitizenConstitutional and administrative law govern the affairs of the state. Constitutional law concerns both the relationships between the executive, legislature and judiciary and the human rights or civil liberties of individuals against the state. Most jurisdictions, like the United States and France, have a single codified constitution with a bill of rights. A few, like the United Kingdom, have no such document. A “constitution” is simply those laws which constitute the body politic, from statute, case law and convention. A case named Entick v Carrington^[173] illustrates a constitutional principle deriving from the common law. Entick’s house was searched and ransacked by Sheriff Carrington. When Entick complained in court, Sheriff Carrington argued that a warrant from a Government minister, the Earl of Halifax, was valid authority. However, there was no written statutory provision or court authority. The leading judge, Lord Camden, stated:

The great end, for which men entered into society, was to secure their property. That right is preserved sacred and incommunicable in all instances, where it has not been taken away or abridged by some public law for the good of the whole … If no excuse can be found or produced, the silence of the books is an authority against the defendant, and the plaintiff must have judgment.^[174]

The fundamental constitutional principle, inspired by John Locke, holds that the individual can do anything except that which is forbidden by law, and the state may do nothing except that which is authorised by law.^[175][176] Administrative law is the chief method for people to hold state bodies to account. People can sue an agency, local council, public service, or government ministry for judicial review of actions or decisions, to ensure that they comply with the law, and that the government entity observed required procedure. The first specialist administrative court was the Conseil d’État set up in 1799, as Napoleon assumed power in France.^[177]

A subdiscipline of constitutional law is election law. It deals with rules governing elections. These rules enable the translation of the will of the people into functioning democracies. Election law addresses issues who is entitled to vote, voter registration, ballot access, campaign finance and party funding, redistricting, apportionment, electronic voting and voting machines, accessibility of elections, election systems and formulas, vote counting, election disputes, referendums, and issues such as electoral fraud and electoral silence.

Criminal law

Criminal law, also known as penal law, pertains to crimes and punishment.^[178] It thus regulates the definition of and penalties for offences found to have a sufficiently deleterious social impact but, in itself, makes no moral judgment on an offender nor imposes restrictions on society that physically prevent people from committing a crime in the first place.^[179][180] Investigating, apprehending, charging, and trying suspected offenders is regulated by the law of criminal procedure.^[181] The paradigm case of a crime lies in the proof, beyond reasonable doubt, that a person is guilty of two things. First, the accused must commit an act which is deemed by society to be criminal, or actus reus (guilty act).^[182] Second, the accused must have the requisite malicious intent to do a criminal act, or mens rea (guilty mind). However, for so called “strict liability” crimes, an actus reus is enough.^[183] Criminal systems of the civil law tradition distinguish between intention in the broad sense (dolus directus and dolus eventualis), and negligence. Negligence does not carry criminal responsibility unless a particular crime provides for its punishment.^[184][185]

Adolf Eichmann (standing in glass booth at left) being tried and sentenced to death by the Israeli Supreme Court in 1961, an example of a criminal law proceedingExamples of crimes include murder, assault, fraud and theft. In exceptional circumstances defences can apply to specific acts, such as killing in self defence, or pleading insanity. Another example is in the 19th-century English case of R v Dudley and Stephens, which tested a defence of “necessity“. The Mignonette, sailing from Southampton to Sydney, sank. Three crew members and Richard Parker, a 17-year-old cabin boy, were stranded on a raft. They were starving and the cabin boy was close to death. Driven to extreme hunger, the crew killed and ate the cabin boy. The crew survived and were rescued, but put on trial for murder. They argued it was necessary to kill the cabin boy to preserve their own lives. Lord Coleridge, expressing immense disapproval, ruled, “to preserve one’s life is generally speaking a duty, but it may be the plainest and the highest duty to sacrifice it.