The patents’ nationality in case of joint ownership is determined by Article 7 of Regulation 1257/2012 which states:
« 1. As an object of property, the European patent with unitary effect shall be treated in its entirety and in all participating Member States as a national patent of the participating Member State in which it has unitary effect and where, according to the European Patent Register
a) the applicant had his domicile or principal place of business on the filing date of the European patent application; or
b) where point a) does not apply, the applicant had a place of business on the date of filing of the European patent application.
2. If two or more persons are entered in the European Patent Register as co-applicants, paragraph 1. a) shall apply to the first co-applicant entered. Otherwise, paragraph 1.a) shall apply to the next co-applicant in the order of entry. Where paragraph 1.a) does not apply to any of the co-applicants, paragraph 1.b) shall apply accordingly.
3. If no applicant is domiciled, has his principal place of business or has an establishment in a participating Member State in which the patent has unitary effect for the purposes of paragraph 1 or 2, the European patent with unitary effect as an object of property shall be treated in its entirety and in all participating Member States as a national patent of the State in which the European Patent Office has its seat, in accordance with Article 6(1) EPC.
4. The acquisition of a right may not depend on an entry in a national patent register.”