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Law School Case Brief

AMP, Inc. v. United States - 182 Ct. Cl. 86, 389 F.2d 448 (1968)


The essence of legal estoppel that can be found in the estoppel of the implied license doctrine involves the fact that the licensor (or assignor) has licensed (or assigned) a definable property right for valuable consideration, and then has attempted to derogate or detract from that right. The grantor is estopped from taking back in any extent that for which he has already received consideration. 


Plaintiff and defendant government had a contract whereby plaintiff would develop and supply a wire-splicing tool. The models were accepted, thus completing the contract. Under a contract provision, defendant was given a royalty-free license to practice the invention that was the subject matter of the patent. Defendant then awarded contracts for the production of the tool and received a quantity of it, while plaintiff acquired another patent. Plaintiff then brought suit under 28 U.S.C.S. § 1498 claiming that the purchase of tools by defendant infringed upon plaintiff's after-acquired patent.


Did an inventor create implied license to practice the invention, which allowed the government to purchase the patented tools from entities other than the inventor?




The court ruled in favor of defendant, holding that plaintiff had granted to defendant, under a contract provision, the right to practice and have practiced the idea embodied by the tool. On this basis, defendant's purchasing was then licensed by implication under the after-acquired patent so as to protect the specific rights granted to it by its contract with plaintiff.

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