On the other hand, it must be noted that the CAFC has held that proving "enablement" of prior art under 102(a) or 102(b) requires less than proving enablement for 35 U.S.C. 112P1 purposes.
Also, as we know, the burden is on applicants and patentees to prove that a prior art reference is inoperable. But the CAFC has set that bar quite high.
The most interesting case in this regard is Rasmussen:
In Rasmussen (an interference), the Board found a patent valid in view of 102(b) art, a published EP application, because (the Board concluded) the EP application was not enabled. The Board made two key findings of fact to support its conclusion: (1) there was no reasonable scientific basis for a person of ordinary skill in the art to conclude that the method in a prior art EP application would be effective [in treating prostate cancer]; and (2) a person of ordinary skill in the art as of the publication date of the EP patent would not have believed that the method described in the patent would be effective.
The CAFC **overturned* the conclusion of non-enablement based on those findings of fact, stating that "Under the legal standard set forth in Hafner and the cases that have followed it, those findings are insufficient to support the Board’s conclusion that EP ’383 is not an enabling reference
for purposes of anticipation."
In other words, a prior art method is enabled even if the reference which discloses the method "teaches away" (only relevant for obviousness); even if the reference states flat out that the method does not yield successful results; and even if as of the date of publication of the reference nobody skilled in the art believed that the method could yield the results later obtained by the patentee.
That's a very low standard.