Licensee estoppel was a U.S. patent law doctrine, now overturned, that a licensee under a patent would not be permitted to challenge the validity of the patent. The Supreme Court, in Lear, Inc. v. Adkins

Lear, Inc. v. Adkins

Lear, Inc. v. Adkins, 395 U.S. 653 , is a decision of the U.S. Supreme Court overturning the doctrine of licensee estoppel and holding that public interest considerations require that licensees be free to challenge the validity of possibly spurious patents under which they are licensed. This...

(1969), held the doctrine inconsistent with a federal policy that the invalidity of specious patents should be unmasked in order to permit full and free competition in technology ideas that belong in the public domain.