In rem: Information from Answers.com
In rem is Latin for "in a thing". In a lawsuit, an action in rem is directed towards some specific piece of property, rather than being a claim for, say, monetary compensation against a person (which is an in personam or personal action). It focuses on proprietary title to property. Land is an example of a case where, when the title (e.g. who owns a house) is in dispute, an in rem action is used to deliver the land itself back to the rightful owner.
The distinction between an in rem action and an in personam action is relevant to which jurisdiction a court case may need to be filed, for the purposes of conflict of laws and civil procedure. An in rem action means that the right jurisdiction would be where the property actually is.
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