Under 35 U.S.C. 312(a)(2) and 37 CFR § 42, all "real parties in interests" (RPIs) are required to be named in an Inter Partes Review petition. Failure to name all RPIs could result in denial of a petition. The policy behind this requirement is rooted in the estoppel provisions that apply to decisions by the Patent Trial and Appeal Board ("PTAB"). Namely, a final written decision by the PTAB estops the petitioner (or all real parties in interest) and their privies from asserting invalidity or unpatentability on any ground that the petitioner raised or "raised or reasonably could have raised" during the IPR or PGR proceeding in a district court, International Trade Commission, or other USPTO proceeding. See 35 U.S.C. 315(e)(1), as amended, and 35 U.S.C. 325(e)(1). The PTO has also identified potential conflicts of interest and credibility of evidence as reasons for requiring the identification of all RPIs.
However, there is no clear definition for what constitutes a RPI. Indeed, the lack of a clear standard was by design due to the highly fact-dependent nature of determining who constitutes a real party in interest:
Who constitutes a real party in interest or privy is a highly fact-dependent question, especially on the issue of whether a party who is not a named participant in a given proceeding nonetheless constitutes a "real party in interest" or "privy" to that proceeding. Courts and commentators agree that there is no "bright-line test" for determining the necessary quantity or degree of participation to qualify as a "real party in interest" or "privy" based on the control concept. See Gonzalez v. Banco Cent. Corp., 27 F.3d 751, 759 (1st Cir. 1994); see also Wright & Miller § 44512 ("The measure of control by a nonparty that justifies preclusion cannot be defined rigidly."). Accordingly, the Office has not enumerated particular factors regarding a "control" theory of "real party in interest" or "privy" in the proposed rules. Instead, to resolve a real party in interest or privy dispute that may arise during a proceeding, the Board plans to consider each case on its specific facts.