The following expression comes directly from the 1st article of a statute:
È costituita per volontà del signor XX ... una Fondazione...
Do you think I could translate this as:
A Foundation ... is constituted at the request of Mr XX... ?
I realise that 'will' and 'request' are two different things, but the general idea is that Mr XX wanted to establish the foundation. 'By the will of ...' almost suggests that the establishment of the foundation was stipulated in Mr XX's 'testamento'.