The contribution starts with the Church's fundamental declarations on its action in the world, analysing their magisterial and canonical foundations, and then dwells on the subject of the exercise of the right of legation and the mediation role of the Holy See in conflicts between third parties. It then proceeds with a survey of the recent negotiating activity of the Catholic Church itself, focusing in particular on the globalisation of concordat law. The aim, in particular, is to highlight the insights that show the attention towards an 'open' and 'enlarged' bilateralism. And conducting a similar screening with respect to the more specific phenomenon of the Holy See's renewed commitment to multilateralism (alongside the internationally relevant 'traditional bilateralism').