The Federal Circuit recently reversed a PTAB determination on remand that a patent was obvious over applicant admitted prior art (“AAPA”) in combination with prior art patents, holding that expressly designating AAPA as a “basis” for a ground is improper under 35 U.S.C. § 311(b). In doing so, the Court rejected the PTAB’s “blanket rule” that “AAPA used in combination with prior art patents or printed publications under § 311(b) is ipso facto not the basis or part of the basis of a ground.” Ultimately, while the case clarifies that expressly listing AAPA in an IPR ground is improper, the precise line between proper and improper uses of AAPA in other instances remains unclear.