Definition
A pipe line is a connected series of pipes laid upon or beneath the surface of the earth for the continuous transportation of oil, natural gas, water, or other substances over distance. In law, the term encompasses not only the physical infrastructure but also the bundle of rights associated with its construction and operation — including easements, rights-of-way, and the authority to occupy private or public land.
The legal significance of pipe lines turns on two related questions: whether the construction and operation of a pipe line constitutes a public use sufficient to support the exercise of eminent domain, and whether a pipe line company qualifies as a common carrier or public utility subject to regulation.
Common Confusion
PIPE LINE vs. PIPELINE: The two-word form ("pipe line") appears consistently in older legal and regulatory texts; the single-word form ("pipeline") dominates modern usage. Researchers searching historical statutes, cases, and secondary sources must use both forms. The split is purely orthographic and carries no legal significance, but failure to account for it will produce incomplete search results in historical corpus materials.
PIPE LINE vs. EASEMENT: A pipe line is the physical and operational thing; an easement (or right-of-way) is the legal instrument authorizing its placement across another's land. These are distinct but inseparable in practice. A pipe line company typically acquires an easement by grant, purchase, or condemnation — it does not acquire fee simple title to the land it crosses.
Why It Matters in Research
The central research question for pipe lines is nearly always eminent domain and public use. Whether a private oil or gas pipe line company may condemn private land turns on whether its operations serve a sufficiently public purpose — a question answered differently across states and eras.
The historical treatment of pipe lines in the courts shifted substantially in the late nineteenth and early twentieth centuries. Early decisions treated oil pipe lines as purely private enterprises serving no public use. Later decisions, influenced by the growth of the petroleum industry and state legislation designating pipe line companies as common carriers, held that condemnation authority was constitutionally permissible. Researchers working with cases from the 1880s through the 1920s will find these competing lines of authority actively in conflict.
The regulatory classification of pipe lines as common carriers — obligating them to transport for the public on non-discriminatory terms — is equally significant and not automatically co-extensive with condemnation authority. A company may be a common carrier for rate-regulation purposes without having eminent domain power, or vice versa, depending on the jurisdiction and statute.
Jurisdictional variation is heavy. Some states extended eminent domain and common carrier status to oil pipe lines by statute relatively early; others resisted. Natural gas pipe lines attracted federal regulatory interest earlier than oil pipe lines, particularly after the Natural Gas Act of 1938. Water pipe lines operated by municipalities occupy different legal ground than privately owned petroleum lines.
Researchers should also be alert to the distinction between interstate pipe lines (subject to federal jurisdiction) and intrastate pipe lines (subject to state law). This distinction became legally critical in the early twentieth century and restructured the entire regulatory landscape. Sources predating that federal-state division will not reflect it.
Historical Dictionary Support
Bouvier's Law Dictionary defines a pipe line as "a connected series of pipes for the transportation of oil, gas, or water" and, more specifically, "a line of pipes running upon or in the earth carrying with it the right to the use of the soil in which it is placed." Bouvier explicitly links pipe lines to eminent domain, stating that "the right to construct a pipe line is a public use, as is also that of laying pipes for a proper purpose in the streets of a city."
Bouvier's treatment reflects the settled position that had emerged by the time of his later editions — that pipe line construction, at least in certain contexts, satisfies the public use requirement. The entry's reference to a California decision (95 Cal. 92) grounds this in contemporaneous authority. However, Bouvier's entry is brief and does not capture the contested nature of the public use question across jurisdictions in the preceding decades, nor does it address the common carrier classification issue in depth. Researchers should treat Bouvier as reflecting a majority or emerging consensus position rather than a universally settled rule.
No other historical law dictionaries in the Law Mind corpus contain dedicated entries for pipe lines. The absence is itself informative: the legal treatment of pipe lines as a distinct subject is a product of industrial-era litigation and legislation, not common law tradition, and dictionary coverage lagged behind the courts.
Jurisdictional Note
State law governs whether a private pipe line company holds eminent domain authority, and statutes vary significantly. Some states expressly confer condemnation power on oil and gas pipe line companies designated as common carriers; others limit condemnation to entities serving demonstrable public needs. Federal jurisdiction over interstate natural gas and oil pipe lines developed through successive statutes and preempts contrary state regulation in those contexts.
Encyclopedia Cross-Reference
The Law Mind Constitutional Law Encyclopedia: The Veto Power — Line-Item Veto, Pocket Veto, and Constitutional Limits [not directly relevant; see instead Eminent Domain entries]
The Law Mind Insurance Law Encyclopedia: Surplus Lines and Non-Admitted Insurance [not relevant]
Note: Neither matched encyclopedia entry bears on pipe lines. Researchers should consult the Eminent Domain and Public Use entries in The Law Mind Constitutional Law Encyclopedia and the Public Utilities and Common Carriers entries in The Law Mind Administrative Law Encyclopedia for the directly applicable doctrinal context.