You can, you just have to ask the board like at any other club, but there isn't much point as you can only sign Basque players, although it can be useful to scout the French-Basque players (I did it on my Bilbao save and found a few good French players I wouldn't of found otherwise). You may have to wait a bit until you have a high job security/board confidence though!
a okay. i have ask them already a thousand times! but i am also at the beginning of the season. how long took it for you, before they say yes? it is kind of strange, even with a team like real sociedad you can scout worldwide!