Ex parte Baurin Got It Wrong, and Startup Patent Portfolios Will Pay for It

By Babak Akhlaghi on September 12, 2026.  In August 2026, the USPTO’s Appeals Review Panel issued its decision in Ex parte Baurin. The panel, led by Director John Squires, reversed the Patent Trial and Appeal Board and reinstated OTDP rejections against a pending application.

Here is the part that should get your attention as a founder. The rejected claims would have expired roughly five years before the reference patent used against them. There was no risk of extending anyone’s monopoly. The panel sustained the rejection anyway, resting on what courts call the anti-harassment rationale.

I advise startups on patent strategy every week, and I think the panel got this wrong. I want to walk you through why, and then show you two related traps that founders fall into long before a decision like this ever touches them.

What Obviousness-Type Double Patenting (OTDP) Actually Protects Against

The bargain behind US patent law is simple. You disclose your invention to the public, and the government gives you twenty years of exclusivity, measured from your earliest effective filing date. After that, the public gets to use it freely.

Obviousness-type double patenting, or OTDP, exists to protect that bargain. You get one patent per invention. You do not get to file a second application on a trivial variation of the same idea and use that second filing to stretch your exclusivity past the twenty-year mark.

I support that doctrine completely. It keeps the system honest.

The problem in Baurin is that the doctrine got applied where its core purpose was absent. The pending application had an earlier effective filing date than the reference patent. Any patent issuing from it would expire first. Issuing those claims extends nothing.

Where the ARP Went Off Course

The panel distinguished the Federal Circuit’s 2024 Allergan decision, which held that a first-filed, first-issued, later-expiring claim cannot be invalidated by a later-filed, later-issued, earlier-expiring reference claim sharing a priority date. The panel read that holding narrowly, keying on actual filing dates rather than effective filing dates.

In my view, the effective filing date should be the threshold question for any OTDP analysis. If the reference patent’s effective filing date comes after yours, your application cannot extend that patent’s life. The analysis should end right there.

Instead, the panel leaned on a second justification. The anti-harassment rationale says that two patents on obvious variants create a risk if ownership ever splits, because an infringer could face separate lawsuits from separate owners.

To be fair to the Director, the decision itself acknowledges the tension. The panel wrote that it would not treat hypothetical harassment as a standalone basis for rejections if it were free to do so, and it openly invited the Federal Circuit to clarify the law. The issue is already headed to the court in In re Ablynx. Until that clarification arrives, examiners will keep making these rejections.

Why This Matters for Your Startup Patent Strategy

If anti-harassment stands alone as a basis for OTDP, every improvement patent in your family becomes a potential weapon against your foundational patents. That includes continuations, continuations-in-part, and standalone improvement applications that share even one inventor with your core filing.

Picture the scenario I worry about most. An engineer helps invent your core technology, then leaves for another company and files an improvement there. Under the reasoning in Baurin, that later application can become an OTDP reference against your original, earlier-filed application.

A terminal disclaimer is the normal cure for OTDP. It requires you to promise two things. Your patent will expire no later than the reference patent, and the two will remain commonly owned. When your former engineer’s improvement belongs to a different company, common ownership is gone and the cure is unavailable.

That puts the startup in a difficult position. You can negotiate to reacquire ownership of the improvement, which is expensive and gives the other side all the leverage. Or you can amend your original claims to distinguish over the reference, giving up the broadest scope you should be entitled to for your own foundational invention.

Neither option is fair, and the doctrine’s stated purpose is not served by either one.

Licensing Is a Starting Line

The Baurin trap involves transferring ownership. There is a parallel trap in licensing, and I have analyzed a case that shows exactly how it plays out.

A patent owner built up eleven licensees over the years. None of the license agreements required the licensees to mark the patented products with the patent number. One agreement expressly stated the licensee had no obligation to mark.

Years later, the patent owner sued a competitor. The competitor raised the marking statute, 35 U.S.C. § 287(a), which cuts off all damages that accrued before the infringer received notice if patented articles went unmarked. The patent owner argued that it sold no products itself – so marking statue doesn’t apply.

The Court disagreed. The marking obligation extends to anyone selling patented products under you, and that includes your licensees. Because the patent owner made no reasonable effort to ensure marking, it lost every dollar of pre-suit damages. In August 2026, the Federal Circuit affirmed that same principle in VDPP v. Volkswagen.

Signing a license is not the finish line. It is the first day of a compliance obligation most founders do not know they have. Build marking, audit, monitoring, and enforcement provisions into every agreement before you sign — and document your compliance work throughout the life of the deal. That record is what you show a judge when you need pre-litigation damages to mean something. But licensing at least keeps ownership intact. The harder problem is when ownership moves — and that starts with who signed your assignment agreements before they walked out the door.

The Assignment You Forgot to Get

The single most important document in your patent strategy is the assignment agreement signed before your first engineer leaves.

Seed-stage founders rarely get this right. The fix is straightforward. Obtain one broad assignment from every inventor that covers two things.

• The invention described in your core application.
• Any continuation application to be filed therefrom.

With that assignment in hand, your team can leave and you can still file continuations from your core application. If an OTDP rejection arrives between family members, you own both applications and a terminal disclaimer resolves it cleanly. The Baurin decision does not disturb ordinary continuation practice for a startup that holds proper assignments.

The exposure sits with improvements. Your core technology evolves, and improvements developed after an inventor departs belong to their new employer. So act fast. File your applications while your inventors are still with you, and paper the assignments the same week.

Clean assignment records also carry direct financial weight. Diligence teams check the chain of title in every financing and acquisition, and gaps in that chain slow deals, weaken valuations, and create leverage for the other side.

Before You Split Your Portfolio, Stop

If you are heading into an acquisition or a partial portfolio sale, ask one question before anything else. Determine whether you are transferring improvements to your core technology while keeping the foundational patents.

Under Baurin, that structure creates a trap. The transferred improvement patents can be asserted as OTDP references against the foundational patents you kept, and the terminal disclaimer path is closed because common ownership ended at closing.

Most founders in a deal focus on valuation, earnouts, and equity. The portfolio split feels like a line item. That line item can quietly undermine the patents you kept.

Founder FAQ

What is obviousness-type double patenting in plain English?

It is a rule preventing you from getting a second patent on the same invention or obvious variations of a first patent, thereby extending the period of exclusivity granted to you by virtue of your first patent.

What does a terminal disclaimer do, and when does it hurt me?

It overcomes an OTDP rejection by promising your second patent expires no later than your first patent and stays commonly owned with it. Terminal disclaimer becomes unavailable entirely once the ownership between the two patents splits.

What happens if I sell part of my patent portfolio?

If the sold patents cover obvious variants of the patents you kept, the sold patents can become OTDP references against your remaining portfolio. You will be unable to file a terminal disclaimer because the patents are no longer commonly owned. Structure the deal with this risk in mind before you sign.

What is the patent marking requirement and why should I care?

Under 35 U.S.C. § 287(a), patented products must be marked with the patent number. Failure to mark eliminates all damages for infringement occurring before the infringer received actual notice. The obligation covers your licensees’ products, and you must take reasonable steps to ensure they comply.

What should my inventor assignment agreements cover?

All right, title, and interest in the core application, plus continuations, divisionals, continuations-in-part, reissues, and foreign filings. Get signatures before anyone departs. Retroactive assignments invite demands for additional compensation and complicate diligence.

Do method-only patents need to be marked?

Method claims alone are exempt because there is no physical article to mark. Courts have cut damages for entire patents where apparatus or system claims were asserted alongside method claims, so mixed portfolios still require marking discipline.

Does Baurin change anything for startups filing continuations today?

With proper assignments in place, ordinary continuation practice remains safe. The new risk sits with improvements owned by departed inventors’ new employers and with portfolio splits during deals. The Federal Circuit will likely clarify the anti-harassment rationale in In re Ablynx, and I expect and hope the Court makes the effective filing date the threshold question and the anti-harassment a secondary concern that should not be given weight unless the primary concern, the patent term extension, is also present in the case.

Talk to a Patent Attorney Before the Next Deal, Not After

Every trap in this article shares one root. A founder optimized for the deal in front of them without asking what that deal does to everything that comes after.

The fixes are cheap early and expensive late. An assignment signed this week costs almost nothing. Reacquiring a patent from a former employee’s new company costs whatever they decide to charge.

If you are building a patent family, negotiating your first license, or structuring an acquisition that touches your portfolio, bring in a patent attorney for startups before the documents are drafted. I review portfolio structures, license terms, and assignment chains with founders regularly, and the earlier that conversation happens, the more options you keep.