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; for example, 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.

International principles.

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:

treaty jurisdiction — An international treaty explicitly decides the issue.

territorial principle — A country asserts jurisdiction over people, property, and events taking place on its own territory.

nationality principle — A country asserts jurisdiction over the conduct of its citizens, anywhere in the world.

passive personality principle — A country asserts jurisdiction over acts committed against its citizens, anywhere in the world.

protective principle — A country asserts jurisdiction over issues that affect its interests, such as conspiracies to overthrow its government, or resources critical to its economy (such as access to an international waterway)

universal jurisdiction — A country asserts jurisdiction over certain acts committed by anyone, anywhere in the world. Usually reserved for exceptionally serious crimes, such as war crimes and crimes against humanity.