This could cause trouble, if the stadiums already have contracts.....
It is already causing trouble. Especially in Bavaria, where the local beer is regarded a vital part of national idiocy... er... identity.
In some places selling alcohol within the stadium isn't allowed anyway, so there are no local contracts with breweries.
In other cases, I think the contracts are mostly with the club usually playing there and hence won't apply. However, I fear every contractor insisting on his local right will face the thread of "his" stadium being excluded from the tournament.

but what about pubs and shops by the stadiums?
AFAIK they are not allowed to sell anything else within a mile of the stadium. Farer away is OK, but how to bring it in the stadium, using only "soft" containers (plastic bottles etc.)?


I'll be more enthusiastic about encouraging thinking outside the box when there's evidence of any thinking going on inside it.
(Terry Pratchett)