Marking Estoppel Law and Legal Definition

Marking estoppel is an equitable doctrine that prevents a party from asserting that a product is not covered by a patent if that party has marked the product with a patent number.

Many courts have applied marking estoppel to prevent defendants from arguing non-claimant of the patented product. [Sliptrack Sys. v. Metal Lite, Inc., 2003 U.S. Dist. LEXIS 26099 (C.D. Cal. Dec. 9, 2003)]