527 U.S. 150 (1999)
In the mid-1990s respondents applied for a patent on a method for increasing computer security.1 A PTO patent examiner rejected the application on the ground that the method was obvious in light of prior art.2 The Board of Patent Appeals and Interferences upheld the examiner's rejection.3
Respondents sought review in the Federal Circuit.4 A three-judge panel treated the question of what the prior art teaches as one of fact and held the PTO's finding clearly erroneous.5 The Federal Circuit then reheard the case en banc to address the standard-of-review question that had divided its panels.6
The en banc court concluded that Federal Rule of Civil Procedure 52(a)'s clearly erroneous standard governs Federal Circuit review of PTO fact findings.7 The Commissioner of Patents petitioned for certiorari, which the Supreme Court granted to decide whether APA review standards control instead.8
The PTO is an agency whose fact findings constitute agency action.9 Before the APA's 1946 enactment the Court of Customs and Patent Appeals reviewed such findings in 89 reported cases, using phrases such as manifest error or clearly wrong.10 The Federal Circuit and supporting amici identified those cases as evidence of a pre-APA tradition of stricter review.11
Whether the Administrative Procedure Act applies when the Federal Circuit reviews findings of fact made by the Patent and Trademark Office?12
Yes. The PTO is an agency whose fact findings constitute agency action, so a reviewing court must apply the APA's court/agency review standards in the absence of an exception under 5 U.S.C. §559.15 The Federal Circuit's claim for an exception based on a pre-APA tradition of stricter review fails because the 89 cases do not reflect a well-established stricter court/court standard of judicial review for PTO factfinding.16 Those cases used phrases such as manifest error or clearly wrong to signal deference to the PTO as an expert body that had reviewed the matter at multiple levels, reasons that support court/agency rather than court/court review.17
Consequently, the APA framework applies to the Federal Circuit's review of PTO fact findings.18
The Administrative Procedure Act applies when the Federal Circuit reviews findings of fact made by the Patent and Trademark Office.19
Related opinions on this issue
Chief Justice Rehnquist dissented on the ground that the en banc Federal Circuit and the patent bar had concluded that the stricter clearly erroneous standard was an additional requirement recognized by law.20 He would defer to the specialized Article III court charged with review of patent appeals rather than independently reexamining the 89 cases.21 Rehnquist also rejected the notion that §559 imposes a clear statement rule on antecedent common-law requirements, as the text preserves requirements otherwise recognized by law without demanding that they be clearly recognized.22