Absolutely untrue, at least if your implication is that they are ONLY relevant in privacy debates. And that would seem to be the implication, since otherwise, what’s the relevance of disabusing me about the applicability of the term?
Antitrust: “…(1) whether the practice, without necessarily having been previously considered unlawful, offends public policy as it has been established by statutes, the common law, or otherwise—whether, in other words, it is within at least the penumbra of some common-law, statutory, or other established concept of unfairness…” FTC v. Sperry and Hutchinson Co., 405 US 233 at FN 5 (1972)
Patent infringement: “The doctrine of equivalence casts around a claim a penumbra which also must be avoided if there is to be no infringement.” Autogiro Company of America v. U.S., 384 F. 2d 391, 400, Court of Claims (1967)
Due Process/Privileges and Immunities: “The notion that the Constitution, through some penumbra emanating from the Privileges and Immunities Clause and the Commerce Clause, establishes this Court as a Platonic check upon the society’s greedy adherence to its traditions can only be described as imperious.” Burnham v. Superior Court, 495 US 604 (1990), Stevens, J., concurring at FN 5.
Labor Management Relations: “The Labor Management Relations Act expressly furnishes some substantive law. It points out what the parties may or may not do in certain situations. Other problems will lie in the penumbra of express statutory mandates. Some will lack express statutory sanction but will be solved by looking at the policy of the legislation and fashioning a remedy that will effectuate that policy. The range of judicial inventiveness will be determined by the nature of the problem.” Complete Auto Transit, Inc. v. Reis, 451 US 401, 407 (1981), quoting Textile Workers v. Lincoln Mills of Alabama, 353 US 448, 458 (1957).