On September 16, 2011, US President Obama has signed the “America Invents Act” (AIA), i.e. a pivotal reform of the US patent law.

Among other things, the AIA has introduced a new procedure called “post-grant review”. While this procedure appears to be partly inspired by the European opposition, there are quite a few differences between the two. Here we highlight some of the currently most evident differences.

As a first similarity, both post-grant reviews and the European oppositions must be filed within 9 months from the grant of the patent.

Furthermore, if a third party starts a nullity action against a US patent after it has also filed a post-grant review, the nullity action is suspended ex officio. Similarly, in Germany the patent law explicitly prohibits starting an invalidity action against a European patent while it is still possible to file an opposition at the EPO, or while such opposition is ongoing.

On the other hand, while post-grant reviews may be requested only by really interested third parties, currently European oppositions can also be filed by a “strawman” and yet remain admissible. Thus, the EPC allows an opponent to hide its identity while challenging a European patent, which may be of interest in certain commercial situations.

In the initial phase of the procedure, the USPTO has the right not to institute a post-grant review where the requester has not already sufficiently demonstrated that at least one of the challenged claims is “more likely than not” unpatentable. Contrary to this, for an opposition to be admissible it is sufficient if it complies with certain formal requirements. In addition, the USPTO decision not to institute a post-grant review cannot be appealed, while a finding of formal inadmissibility by the EPO can be appealed.

It is therefore clear that, at least in the initial phase, European oppositions are more easily accessible to third parties than US post-grant reviews. In terms of evidence, during a post-grant review the USPTO may order discovery (albeit more limited than that possible in a US lawsuit). In contrast, in a European opposition is essentially up to the opponent to find the necessary evidence to prove the invalidity of the patent, with virtually no ability to compel the patentee to provide any evidence in his sole possession.

In addition, while a post-grant review can also be brought against a reissued US patent, an opposition cannot be brought against a European patent after a limitation thereof at the EPO by the owner of the patent itself.

The above means that under certain circumstances European patent are less vulnerable to third party attacks than US patents.

Finally, one of the main grounds of opposition at the EPO is the extension of the subject-matter of the patent beyond the content of the original application. On the other hand, this does not seem to be a possible ground for revocation in post-grant reviews. As is known, the EPO is very strict when assessing whether a patent has been amended so as to extend its subject-matter beyond the content of the original application, with hundreds, if not thousands, of European patent regularly revoked on the basis of this single ground.

In this respect, oppositions at the EPO thus offer a possibility to challenge European patents which is not available in the US.

It thus appears that in many respects European oppositions are, depending on the circumstances, more user-friendly than the new US post-grant reviews, both from the patentee’s and from the opponent’s point of view.

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