One knock against the inter partes reexamination system is that it creates an estoppel. Under 35 USC 315(c), a third-party of requester is estopped from later asserting that a claim is invalid based on grounds that were "raised or could have been raised" during the reexamination. The 315(c) estoppel, however, is specifically limited to "civil action[s]" arising from 28 USC 1338 – i.e., those brought in district court. Similarly, under Section 371(b), an accused infringer cannot request an inter partes reexamination after losing a final decision in district court on any validity issues that the party "raised or could have raised" in the civil action.
In an e-mail earlier this week, Scott Kamholz of Foley Hoag raised the idea that the inter partes reexamination estoppel provisions do not apply to Section 337 investigations through the ITC. I believe Kamholz is correct. Thus, an ITC finding of validity does not estop the losing defendant from later requesting inter partes reexamination on the same grounds. Likewise, a defendant may raise invalidity issues in an ITC investigation that were previously addressed by an inter partes reexamination involving the same parties. Of course, the proceedings in the ITC and PTO are quite different and could readily lead to different outcomes. Perhaps most notably, patents are given a strong presumption of validity in ITC proceedings but are not presumed valid during reexamination.