Definition
In general legal usage, migration refers to the movement of persons from one place to another, particularly across national or jurisdictional boundaries, with the intent to take up residence. The term appears most prominently in two contexts:
1. Constitutional usage (historical). In Article I, Section 9 of the U.S. Constitution, "migration" appears alongside "importation" in the clause that prohibited Congress from banning the transatlantic slave trade before 1808. The pairing was deliberate and politically charged: "migration" referred to the voluntary movement of free persons of African descent into the United States, while "importation" referred to the forced transport of enslaved persons as property. The distinction encoded the legal difference between a free person who moved and a chattel that was shipped.
2. Modern immigration law. In contemporary usage, migration is the broad, informal term for the movement of people across borders. It encompasses lawful immigration, unauthorized entry, refugee movement, and temporary relocation. Immigration law as a formal discipline uses more precise terms — immigrant, nonimmigrant, alien, refugee, asylee — but migration serves as the umbrella concept in policy discussion, international law instruments, and comparative legal scholarship.
Common Language
Modern common usage (Wiktionary): An instance of moving to live in another place for a while; also used for seasonal animal movement, cellular movement, and platform transitions in technology.
Historical common usage (Webster's 1913): "The act of migrating."
The gap between common and legal meaning here is not one of definition but of precision and stakes. In ordinary speech, migration is casual and descriptive — people migrate, birds migrate, data migrates. In law, particularly constitutional and immigration law, which persons are classified as migrants (versus immigrants, refugees, or asylees) determines which legal regimes apply, which rights attach, and historically, whether a person was recognized as a legal subject at all.
Common Confusion
Migration vs. Immigration. In legal and policy contexts, immigration typically refers to the movement of persons into a specific country with the intent to remain permanently, and carries with it a body of statutory and regulatory law. Migration is the broader, more neutral term and does not necessarily imply permanence, legality, or a particular destination. International instruments and organizations (such as the International Organization for Migration) use migration to capture the full spectrum of human movement that immigration law, with its sharp distinctions, may not reach.
Migration vs. Importation (constitutional). As Anderson's Dictionary of Law makes explicit, these two terms in Article I, Section 9 were not synonyms. Migration applied to free persons; importation applied to enslaved persons treated as property. Conflating them erases the constitutional text's recognition — however indirect and evasive — that both categories of persons existed and that the legal treatment of each differed fundamentally.
Why It Matters in Research
Researchers working in the Law Mind corpus will encounter migration in at least three distinct registers, and the applicable legal framework shifts dramatically across them.
First, constitutional history. The Article I, Section 9 clause is one of the most carefully obscured provisions in the original Constitution — the framers avoided the word "slavery" entirely. Researchers analyzing antebellum constitutional law, the slave trade, or the legal status of free Black Americans will find that migration in this context is a term of art with a specific meaning reconstructed largely through legislative history and contemporaneous commentary. Anderson's gloss is the essential starting point.
Second, immigration law. Post-1875 federal immigration statutes use immigrant and alien as the operative terms; migration rarely appears as a statutory term of art in U.S. domestic law. Researchers should not assume that historical legal dictionary definitions of migration map cleanly onto modern immigration doctrine. The word appears more often in international law — treaties, conventions, and the instruments of bodies like the ILO and IOM — where it carries its own definitional weight.
Third, internal migration. Some historical legal sources use migration to describe movement within a country — particularly the movement of formerly enslaved persons after emancipation, or westward population movement in the nineteenth century. This usage has no direct modern statutory analog but appears in historical legal commentary, Reconstruction-era legal documents, and early civil rights scholarship. Researchers should read context carefully before assuming a cross-border meaning.
The Bouvier entry's terse redirect to "See IMPORT" is itself instructive: Bouvier treats migration primarily through the lens of the constitutional slave trade clause and the importation of persons as an economic and property question. Researchers relying solely on Bouvier will miss the broader immigration and human-movement dimensions the term acquired after the late nineteenth century.
Historical Dictionary Support
Anderson's Dictionary of Law provides the most substantive historical entry and is worth taking seriously. Its reading of Article I, Section 9 — that migration and importation tracked the free/enslaved distinction — reflects a view held by a number of constitutional commentators and is consistent with the legislative history of the 1808 Act prohibiting the slave trade. This interpretation was not universally settled in the antebellum period, but it represents the stronger historical reading.
Bouvier's redirect to "Import" treats migration as essentially a subsidiary issue of the importation clause, collapsing the free-person dimension that Anderson preserves. This is a meaningful divergence. Researchers using Bouvier as a primary source on this point should supplement with Anderson and with primary constitutional sources.
Neither dictionary addresses migration in the sense that dominates modern legal usage — the movement of persons subject to federal immigration statutes — because the comprehensive federal immigration system postdates both dictionaries' primary editions. The Chinese Exclusion Act (1882) and the Immigration Act of 1891 mark the beginning of that statutory tradition; neither Anderson nor Bouvier captures its development.
Jurisdictional Note
In U.S. law, regulation of migration is a federal matter under the plenary power doctrine; states have limited authority to legislate in this space. In international law, migration is governed by a patchwork of bilateral treaties, regional agreements, and soft-law instruments, with no single binding global framework equivalent to domestic immigration codes.