Does a guilty plea constitute a waiver of all defenses available to the criminal defendant?

We recognize that a plea of guilty does not constitute a waiver of all defenses available to a criminal defendant. See Menna v. New York, 423 U.S. 61, 63 n. 2, 96 S.Ct. 241, 242 n. 2, 46 L.Ed.2d 195 (1975). A guilty plea does, however, constitute an admission of all facts necessary for conviction, as well as a waiver of "all constitutional claims that might have precluded the prosecution from establishing factual guilt had the case gone to trial." Launius v. United States, 575 F.2d 770, 771 (9th Cir.1979).