Before a court can decide a case against someone, it must have authority over them. The analysis has two parts, and the constitutional one does most of the work.

General jurisdiction exists where the defendant is essentially at home — for an individual, their domicile; for a company, its place of incorporation and principal place of business. There the court may hear any claim, related to the forum or not.

Specific jurisdiction requires that the claim arise out of or relate to the defendant’s contacts with the forum, that those contacts be purposeful rather than random or the unilateral act of someone else, and that exercising jurisdiction be reasonable.

What tends to establish it: conducting business in the state, entering contracts to be performed there, directing conduct at residents, and consenting by a forum-selection clause. What tends not to: a passive website accessible everywhere, an isolated purchase, and contacts created solely by the plaintiff.

Practical points. The objection is waived if not raised at the outset, which makes it one of the few defenses that must be asserted immediately. And it is frequently paired with a venue or forum non conveniens argument, since a defendant who cannot defeat jurisdiction may still move the case somewhere more convenient.