Definition
Latin term meaning "immovable." In civil law and conflict-of-laws doctrine, *immobilis* (used in the plural as *immobilia*, or in the fuller phrase *res immobiles*) denotes things that are fixed in place and cannot be moved without losing their essential character or identity — principally land and buildings permanently attached to land. The term is the civil law equivalent of what common law systems call real property or realty. Its significance lies less in the category itself than in the legal consequences that attach to it: immovable property is governed by the law of its physical location rather than the law of the owner's domicile.
Common Confusion
IMMOBILIS is sometimes encountered interchangeably with IMMOBILIA and RES IMMOBILES in historical sources. These are grammatical variants of the same concept, not distinct legal terms. *Immobilis* is the adjectival form; *immobilia* is the nominalized plural (immovable things); *res immobiles* is the full noun phrase (immovable things/objects). Researchers encountering any of these forms in primary or secondary sources are looking at the same underlying doctrine.
Why It Matters in Research
The primary research importance of *immobilis* is its connection to the conflict-of-laws maxim *immobilia situm sequuntur* — immovable things follow their situs, or are governed by the law of the place where they are situated. This principle, prominent in 19th-century American and civilian jurisprudence, determines which jurisdiction's law governs questions of title, succession, conveyance, and encumbrance for real property when multiple legal systems are potentially in play.
Researchers working in 19th-century American legal materials will encounter this term frequently in treatises on conflict of laws and private international law, particularly in Kent's Commentaries and works drawing on Roman and civil law tradition. It appears less often in pure common law court opinions, which tended to express the same concept through the phrase "law of the situs" without invoking the Latin.
The key research trap is assuming *immobilis* belongs exclusively to Roman or civil law contexts. American courts and treatise writers, including Kent, used the term and the underlying situs doctrine broadly — it was treated as a received principle of general jurisprudence applicable in common law courts as well. A researcher finding *immobilis* in an American source should not conclude the source is drawing on foreign or inapplicable authority.
The corpus connection to run down: citations to Kent's Commentaries (particularly volume 2) and to Mackeldey's Roman Law are the standard reference chain in historical sources. Both are well within the Law Mind corpus and can be checked directly for the surrounding doctrinal context.
Historical Dictionary Support
The three source dictionaries are in close agreement. All define *immobilis* as Latin for "immovable" and identify *immobilia* or *res immobiles* as the category of things — lands and buildings — to which it applies. Burrill's adds the most substantive content by stating the maxim *immobilia situm sequuntur* with a brief gloss, and by citing both Mackeldey and Kent. Black's (both editions) cites only Mackeldey and omits Kent and the maxim, which is a meaningful omission given that Kent's treatment of the situs rule was highly influential in American practice.
None of the three dictionaries give extended treatment to the substantive content of the category — that is, what counts as immovable versus movable — which was a live question in civil law doctrine (fixtures, growing crops, servitudes, and certain rights in land generated real classification disputes). Researchers needing that doctrinal depth will need to go to the treatise sources cited, not to the dictionary entries themselves.
Jurisdictional Note
The situs rule encoded in *immobilia situm sequuntur* became a bedrock principle of American conflict-of-laws doctrine regardless of whether a state had civil law roots. Louisiana, with its civilian heritage, applied the concept through the civil law framework directly; common law states applied the functionally identical situs rule through equity and common law reasoning. The terminology differs across jurisdictions; the operative doctrine does not.