Jurisdiction
Scope of Jurisdiction
Jurisdiction refers to the extent and nature of a state’s authority over a particular territory, persons and things passing through it. It is a fundamental principle that a state may only exercise jurisdiction over its territory. It may not exercise jurisdiction in another state without its consent.
The state may exercise jurisdiction in its own territories in relation to things that have taken place abroad. States may pass legislation exercising jurisdiction over things taking place aboard in certain cases. This is subject to the rules of international law limiting the extent to which states may exercise jurisdiction within their territory in respect of such matters.
The common law, and traditionally, most states, did not seek to exercise jurisdiction over matters happening abroad. States reserved the right to charge treason.
Extra-Territorial
The exercise of jurisdiction over matters happening abroad has changed significantly in recent years. The general and strong presumption is that domestic legislation does not have extra-territorial effect unless specifically provided. However, legislation may provide for matters taking place abroad where there is a sufficient connection between the individuals concerned and the state.
Ireland passed legislation permitting the prosecution of offences occurring in Northern Ireland in the Criminal Law Jurisdiction Act, 1976. Legislation against child pornography allows the prosecution of offences committed aboard.
States may prescribe jurisdiction in relation to things happening abroad, which they may enforce within their territory. A state may not take enforcement action in another state other than in accordance with treaties and arrangements with that state.
Limits to Sovereignty
The general principle is that jurisdiction is absolute and complete. States have power over all persons, property and events within their territory. This follows from the nature of sovereignty and the existence of a state apparatus.
States may, by international agreement, allow immunity and freedom to certain persons from the exercise of their jurisdiction. Accordingly, diplomats, and public vessels of other states are granted significant immunity from jurisdiction.
Jurisdiction Issues
The extent of civil and criminal jurisdictions are broadly similar in scope. States may exercise criminal jurisdiction over persons under a number of different principles. It is argued that civil jurisdiction requires some real and direct connection between the state which claims jurisdiction and the subject matter.
There are five principal types of jurisdiction over persons, both natural and corporate bodies, in international law. States may exercise jurisdiction over their nationals as well as on a territorial basis.
States owe duties to the state of proper jurisdiction to refrain from acting in a manner that is inappropriate under international law. There is no reason, however, in principle, why two states may not equally have jurisdiction over the one matter and the same person relating to the same events.
Multi-State Issues
Concurrent jurisdiction may be problematic in some cases.  Generally, the state in whose custody the person concerned has primary rights. However, that state may agree to extradite the person to another state, for example, the one where the particular crime took place.
Questions of double jeopardy may arise if two states exercise jurisdiction over a person in respect of the same crime. The presumption against double jeopardy holds in international law.
Because of the increasingly sophisticated nature of societies and the manner in which crimes may be committed, many states have extended criminal jurisdiction. They typically include cover cases where preparatory acts in the commission of a crime were undertaken within the territory, although the principal or substantial parts were committed abroad.
International Crimes
Some crimes are so heinous that under international law, universal jurisdiction is recognised. Any state may exercise jurisdiction.
Universal jurisdiction exists in relation to piracy, genocide and atrocities. They may be regarded as offences against the law of nations itself. In practice, the suspect is likely to be extradited to the state most closely connected to the crime.
International law allows states to exercise jurisdiction over their nationals wherever the offence or civil wrong takes place. The national is entitled to diplomatic protection from the state and correspondently subject to civil and criminal jurisdiction. Many states exercise jurisdiction for serious crimes such as murder and serious sexual offences on the basis of nationality.
Special Treaties
States may agree by treaty to confer jurisdiction to try offenders. Historically, there were no international bodies having jurisdiction over individuals. After World War II, the Nuremberg and Tokyo war tribunals exercised this kind of jurisdiction.
After the Yugoslavian and Rwandan wars, war crimes tribunals were established by the Security Council. They have tried a number of cases of serious crimes of concern to the international community.
Univerisal Juriscition
A pure universal jurisdiction state might be prepared to act where there is no connection at all with the state other than the physical custody of the individual.
Universal jurisdiction may be exercised for crimes against international law, including war crimes, piracy, genocide, torture, crimes against humanity and hijacking. Certain drug-related offences and air piracy are similarly subject to universal jurisdiction.
States may exercise jurisdiction over matters which may have a deleterious effect on the state, irrespective of where the acts take place or are committed. They may refer to activities of non-nationals.
Actions taken aboard which would have a harmful effect on the state may be the subject of extra-territorial jurisdiction. Accordingly,  a conspiracy outside the state to do something with the state may be prosecuted within the state.
Most states have elements of this protective jurisdiction. It is an accepted basis of jurisdiction and customary international law. It allows the state to deal with extraterritorial acts done by aliens which have an adverse effect on its people,  welfare or security. Principles of international comity may mandate declining jurisdiction.
Broad Extra-Territorial
Some jurisdictions have gone so far as to claim jurisdiction over anything which has effects in its territory. United States Anti-trust legislation is extremely broad in scope, and it has been resisted by many countries.
An entity with some operations in the United States may be subject to heavy penalties for engaging in anti-competitive practices even where they take place wholly outside the United States. This is particularly problematic if the actions and lawful in the state in the actions took place.
The United States is also active in extraterritorial jurisdiction in other areas. It may seek to exercise jurisdiction over nationals of other territories. There is tension between the desires of the states to protect themselves and the interest of other states, together with the general interest minimising multiple jurisdiction over the same matter.
Passive Personality Principle
The passive personality principle looks to the identity of the individual involved in the criminal offence. Under these principles, a state may have jurisdiction over crimes where the victim is a national, irrespective of the place where the crime is committed or the nationality of the person who committed the crime. The principle applies most commonly in respect of criminal jurisdiction, but it may, in principle, apply to civil jurisdiction.
Passive personality jurisdiction is not considered to be necessary to maintain a comprehensive system of jurisdiction under international law. The majority of criminal matters will necessarily fall within the jurisdiction of at least one other state under the above general principles.
The practical effect of the principle is that nationals carry the protection of the law of their home state, wherever they go. Under the principle, all persons who come in contact with him would be subject to the date of his nationality.
Removal Inwards
Many states will refuse to exercise jurisdiction over persons brought into their state by unconventional or unlawful means or where a person’s presence has been procured by an abusive process.
A state may decline jurisdiction on the basis of a breach of the principle of lawfulness if the violation of international law is the reason why the defendant is before the court. The better view is that jurisdiction should not be exercised.
However, this principle does not necessarily hold and many states do not adhere to it. In the famous controversial case involving an alleged war criminal, Israel abducted a person forcefully in violation of Argentina’s sovereignty. Its courts accepted jurisdiction.
International Criminal Courts
The International Criminal Court exercises jurisdiction over the most serious international crimes, including genocide, war crimes, crimes of aggression and crimes against humanity. The court will prosecute only if the domestic courts are unwilling or unable to prosecute. This is the complimentary principle.
The International Criminal Court may have jurisdiction if one or more of the parties is a state party, the accused is a national of a state party, the crime is committed on the territory of the state or the state is not a party to the statute. may decide to accept the court’s jurisdiction over a specific crime that has been committed within its territory or by its national.
Before the court has jurisdiction, the prosecutor must have referred the matter to the court. The Security Council has referred the matter to the prosecutor for the ICC or the prosecutor for the ICC undertake an investigation under its own initiative in accordance with the ICC statute.
Extradition is regulated by a treaty. There is no general international law duty to extradite in the absence of a treaty.
State Immunity
Historically the sovereign and the state were regarded as one. The ruler of a foreign state enjoyed complete immunity for acts done in a  private capacity. However, the modern approach has modified absolute immunity. Immunity is only available for governmental acts, as opposed to commercial and trading acts.
The move towards more restrictive immunity commenced in the 1950s and 60s case law and has developed since then, limiting immunity to sovereign or public acts but not private acts.
The 1972 Convention on State Immunity sets out circumstances in which sovereign immunity is applicable. The UN Convention on jurisdiction and immunities of states and their property 2004  set out general principles of immunity with exceptions. Restrictive immunity in the above sense is now generally accepted.
Foreign Enforcement in State
International law regarding enforcement jurisdiction may not be exercised in the territory of another state without its consent. Enforcement jurisdiction is limited to the territory concerned. States do not generally enforce the public laws of other states.
In the above sense, public law means criminal law, but also taxation and other matters that are traditionally part of the sovereign power rather than rules which provide for rights and duties between individuals such as contract, family and property law/
States may grant exceptionally, jurisdiction to other states to enforce in their territory. Search and pursuit rights may be given in relation to the detection of serious crimes.