Article 175
Preservation of acquired rights

(1) In the event of a State ceasing to be party to this Convention in accordance with Article 172, paragraph 4, or Article 174, rights already acquired pursuant to this Convention shall not be impaired.

(2) A European patent application which is pending when a designated State ceases to be party to the Convention shall be processed by the European Patent Office, as far as that State is concerned, as if the Convention in force thereafter were applicable to that State. 

(3) Paragraph 2 shall apply to European patents in respect of which, on the date mentioned in that paragraph, an opposition is pending or the opposition period has not expired.

(4) Nothing in this Article shall affect the right of any State that has ceased to be a party to this Convention to treat any European patent in accordance with the text to which it was a party.