Article 31

1. [Relations between States bound by this Convention] Between States members of the Union which are bound both by this Convention and any earlier Act of the Convention, only this Convention shall apply.

2. [Possible relations with States not bound by this Convention] Any State member of the Union not bound by this Convention may declare, in a notification addressed to the Secretary-General, that, in its relations with each member of the Union bound only by this Convention, it will apply the latest Act by which it is bound. As from the expiration of one month after the date of such notification and until the State member of the Union making the declaration becomes bound by this Convention, the said member of the Union shall apply the latest Act by which it is bound in its relations with each of the members of the Union bound only by this Convention, whereas the latter shall apply this Convention in respect of the former.