In Natural Alternatives v. Iancu, the Fed. Cir. rejected patentee’s claim to priority under 120 made through a chain of patents which included a continuation-in-part application (CIP).  The CIP application claimed 120 priority through a chain of patents and to a provisional application.  Soon after filing a continuation application properly claiming 120 priority to the CIP, applicants disclaimed 120 priority in the CIP application in order to gain the benefit of a longer patent term.  Patentee’s argument that priority vested when filed, was rejected as confusing a claim to priority with entitlement and that the disclaimer of priority in the CIP broke the chain.  Patentee’s citation to the MPEP section 201.11 that an altered priority claim only affect the instant application, was rejected as a too narrow reading with a reminder that the MPEP does not have the force of law.  The Fed. Cir. affirmed the long-standing interpretation of priority as a single chain, growing with each additional continuation.  Finally, well understood trade-offs between priority and patent term in CIP applications was acknowledged as not impermissibly limiting applicant’s ability to seek patent protection.  Moral of the story, CIP applications can be more costly on the back end.