Personal jurisdiction

Personal jurisdiction is a court's jurisdiction over the parties, as determined by the facts in evidence, which bind the parties to a lawsuit, as opposed to subject-matter jurisdiction, which is jurisdiction over the law involved in the suit. Without personal jurisdiction over a party, a court's rulings or decrees cannot be enforced upon that party, except by comity; i.e., to the extent that the sovereign which has jurisdiction over the party allows the court to enforce them upon that party. A court that has personal jurisdiction has both the authority to rule on the law and facts of a suit and the power to enforce its decision upon a party to the suit. In some cases, territorial jurisdiction may also constrain a court's reach, such as preventing hearing of a case concerning events occurring on foreign territory between two citizens of the home jurisdiction. A similar principle is that of standing or locus standi, which is the ability of a party to demonstrate to the court sufficient connection to and harm from the law or action challenged to support that party's participation in the case.

Since there is no world government which all countries recognize to arbitrate disputes over jurisdiction, sovereign powers can find themselves in conflict over which is the more appropriate venue to hear a case, or which country's laws should apply. These conflicts are sometimes resolved de facto by physical factors, such as which country has physical possession of a defendant or property, or sometimes by use of physical police or military force to seize people or property. A country with loose rule of law – for example an absolute monarchy with no independent judiciary – may arbitrarily choose to assert jurisdiction over a case without citing any particular justification. Such assertion can cause problems, such as encouraging other countries to take arbitrary actions over foreign citizens and property, or even provoking skirmishes or armed conflict.

In practice, many countries operate by one or another principle, either in written law or in practice, which communicate when the country will and will not assert jurisdiction:

Different principles are applied by different countries, and different principles may be applied by the same country in different circumstances. Determination of whether or not a court has jurisdiction to hear a case is the first stage of a conflict of laws proceeding, potentially followed by choice of law to determine which jurisdiction's laws apply. Executive prosecutorial authority and foreign policy also play a role in scope and practical impact of jurisdiction choices.

Any assertion of jurisdiction based on anything other than the territorial principle is known as extraterritorial jurisdiction. Prosecution of a case against an out-of-territory defendant is known as assertion of long-arm jurisdiction.

When a person commits a crime in a foreign country against the laws of that country, usually the host country is responsible for prosecution. The Vienna Convention on Consular Relations requires that the host country notify the foreign embassy, potentially allowing the foreign country to assist in legal defense and monitor conditions of detention. (Most countries protect their citizens against foreign powers in general.)

Foreign diplomats enjoy diplomatic immunity in many countries based on the Vienna Convention on Diplomatic Relations or bilateral agreement, and foreign military personnel may be subject to the jurisdiction of their home country based on a status of forces agreement or Visiting Forces Agreement.

If a person is not physically present in the country which wishes to prosecute a case, that country may either wait until the person enters the national territory, or pursue extradition by legal or extralegal means, and with or without a general extradition treaty. Some countries (like China) prefer to prosecute their own citizens for crimes committed abroad rather than extradite them. Other countries defer to the host country.