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The rights guaranteed by implication in a constitution or the implied powers of a rule.

The original and literal meaning of penumbra is "a space of partial illumination between the perfect shadow … on all sides and the full light" (Merriam Webster's Collegiate Dictionary, 10th ed., 1996). The term was created and introduced by astronomer Johannes Kepler in 1604 to describe the shadows that occur during eclipses. However, in legal terms penumbra is most often used as a metaphor describing a doctrine that refers to implied powers of the federal government. The doctrine is best known from the Supreme Court decision of griswold v. connecticut, 381 U.S. 479, 85 S. Ct. 1678, 14 L. Ed. 2d 510 (1965), where Justice william o. douglas used it to describe the concept of an individual's constitutional right of privacy.

The history of the legal use of the penumbra metaphor can be traced to a federal decision written by Justice stephen j. field in the 1871 decision of Montgomery v. Bevans, 17 F.Cas. 628 (9th C.C.D. Cal.). (At the time, Field was performing circuit duty while a member of the Supreme Court.) Since the Montgomery decision, the penumbra metaphor has not been used often. In fact, more than half of its original uses can be attributed to just four judges: oliver wendell holmes, jr., learned hand, benjamin n. cardozo, and William O. Douglas.

In an 1873 article on the theory of torts, Justice Holmes used the term penumbra to describe the "gray area where logic and principle falter." In later decisions, Justice Holmes developed the penumbra doctrine as representing the "outer bounds of authority emanating from a law." Justice Holmes usually used the word in an attempt to describe the need to draw Arbitrary lines when forming legislation. For instance, in the decision of Danforth v. Groton Water Co., Holmes referred to constitutional rules as lacking mathematical exactness, stating that they, "[l]ike those of the Common Law, end in a penumbra where the Legislature has a certain freedom in fixing the line, as has been recognized with regard to the police power" (178 Mass. 472, 476–77, 59 N.E. 1033, 1034 [1901]).

Judge Hand expanded the meaning of the word in opinions written between 1915 and 1950 by using it to indicate the vague borders of words or concepts. He used it to emphasize the difficulty in defining and interpreting statutes, contracts, Trademarks, or ideas.

Justice Cardozo's use of the penumbra metaphor in opinions written between 1934 and 1941 was similar to Holmes's application, but Justice Douglas took a different approach. Rather than using it to highlight the difficulty of drawing lines or determining the meaning of words or concepts, he used the term when he wanted to refer to a peripheral area or an indistinct boundary of something specific.

Douglas's most famous use of penumbra is in the Griswold decision. In the Griswold case, appellants Estelle Griswold, executive director of the Planned Parenthood League of Connecticut, and Dr. C. Lee Buxton, a medical professor at Yale Medical School and director of the league's office in New Haven, were convicted for prescribing contraceptive devices and giving contraceptive advice to married persons in violation of a Connecticut statute. They challenged the constitutionality of the statute, which made it unlawful to use any drug or medicinal article for the purpose of preventing conception, on behalf of the married persons with whom they had a professional relationship. The Supreme Court held that the statute was unconstitutional because it was a violation of a person's right to privacy. In his opinion, Douglas stated that the specific guarantees of the Bill of Rights have penumbras "formed by emanations from those guarantees that help give them life and sub-stance," and that the right to privacy exists within this area.

Since Griswold, the penumbra doctrine has primarily been used to represent implied powers that emanate from a specific rule, thus extending the meaning of the rule into its periphery or penumbra.

Further readings

Greely, Henry T. 1989. "A Footnote to 'Penumbra' in Griswold v. Connecticut." Constitutional Commentary 6.

Helscher, David. 1994. "Griswold v. Connecticut and the Unenumerated Right of Privacy." Northern Illinois University Law Review 15.

Henly, Burr. 1987. "'Penumbra': The Roots of a Legal Metaphor." Hastings Constitutional Law Quarterly 15.

McLaughlin, Gerald. 1999. "Creating a Clear and Unequivocal Standard for Letter of Credit Notices: The Penumbra of the UCP." Journal of Banking and Finance Law and Practice 10 (September): 263–64.

Worsham, Julia B.L. 1999. "Privacy Outside of the Penumbra: A Discussion of Hawaii's Right to Privacy." The University of Hawaii Law Review 21 (summer): 273–315.


Judicial Review; Jurisprudence.


noun brink, cover, edge, fringe, margin, outskirt, reflection, shade, shadow
Associated concepts: penumbra of a ConstitutionalAmendment
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