A "prior national right" or "earlier national right" is a national patent or application which was filed before, but published after the effective filing date of an EP patent or application.
While prior national rights are not considered to be prior art during the examination of an EP application, once the application is granted and validated, any prior national rights existing in a validated state of the patent may be used against the validity of the patent for that state.
The EPO have recently begun conducting "top-up searches" before issuing a Rule 71(3) communication (covered here). The search is designed to identify any existing prior national rights that may be relevant to the set of claims intended for grant. Normally, in response to the Rule 71(3) communication, the claims can be amended for the specific state in which a relevant prior national right has been identified, while the remaining states can maintain the original granted claims. However, with the Unitary Patent Convention (UPC) set to start on 1 June 2023, this strategy will have to be revised.
To obtain a unitary patent, the claims must be identical across all UPC member states. Therefore, the practice of amending the claims in just one validated state will no longer be viable. Additionally, if a unitary patent is successfully invalidated in a single court, it is invalidated across all member states of the UPC. In theory the UPC could greatly increase the power of prior national rights, as a single prior national right could require restricting the claims across all UPC member states, resulting in a narrower scope of protection than would be obtained with the individual national patents of the EPC. The alternative is to brave the risk of protection across the entire region being invalidated. The reason for the new top-up searches could therefore be to aid proprietors in deciding if they should request a unitary patent upon grant, or if a bundle of national patents may offer a better form of protection.
Until the UPC finally comes into effect, you can stay informed with the latest information by visiting Marks & Clerk's UPC resource hub.