(1) A patent is revoked (section 61) if it emerges that
1. the subject matter of the patent is not patentable under sections 1 to 5;
2. the patent does not disclose the invention in a manner sufficiently clear and complete for it to be carried out by a person skilled in the art;
3. the essential content of the patent has been taken from the descriptions, drawings, models, implements or equipment of another person or from a process used by this person without their consent (usurpation);
4. the subject matter of the patent extends beyond the content of the application as filed with the competent authority; the same applies if the patent was granted on a divisional application or on a new application filed under section 7 (2), and the subject matter of the patent extends beyond the content of the earlier application as filed with the competent authority.
(2) Where the grounds for revocation refer only to part of the patent, it is maintained with a corresponding limitation. The limitation may be effected in the form of an amendment of the patent claims, the description or the drawings.
(3) Upon revocation, the patent and the application are deemed not to have had, from the outset, the effects specified. In the event of maintenance with limitation, this provision applies accordingly.