This is an EU Directive designed to prevent one Member State giving an unfair advantage to a particular commercial organisation or sector. For instance if the UK Government were to give subsides to its steel industry, this would distort competitivity across the EU.
I have noticed however that the State Aid principle is being quoted (sometime out of simple lack awareness) by Government officials to block large grants to zoo and botanic sites. There is actually case law and precedent to establish the eligiblity of zoos and similar sites to receive substantial amounts of public money.
If any sites across the EU are having difficulty with this issue, please get in touch, and we can probably help