Personal jurisdiction

Personal jurisdiction is a court's jurisdiction over the parties to a lawsuit, as opposed to subject-matter jurisdiction, which is jurisdiction over the law and facts involved in the suit. If a court does not have personal jurisdiction over a party, its rulings or decrees cannot be enforced upon that party, except by comity; i.e., to the extent that the sovereign having 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.

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 principles, 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.

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Wikipedia