In Data Engine Technologies LLC, v. Google LLC, Case No. 21-1050 (Fed. Cir. 2021), the Court of Appeals for the Federal Circuit affirmed the district court’s holding that a patentee cannot first argue a preamble limitation contains patent eligible subject matter and then later argue that the same term is non-limiting. The CAFC noted that analogous to a patentee who “relies on language found in the preamble to successfully argue that its claims are directed to eligible subject matter…cannot later assert that the preamble term has no patentable weight for purposes of showing infringement,” a patentee’s emphasis on a preamble term in support of patent eligibility precludes the patentee from arguing later that the preamble has no weight.
Opinion can be found here: http://www.cafc.uscourts.gov/sites/default/files/opinions-orders/21-1050.OPINION.8-26-2021_1825229.pdf