To be fair to Apple there wasn't a clear precedent set before this.
There definitely is now though and you can be sure legal teams around the world will be advising senior leadership teams to rearrange their corporate structures accordingly.
The whole situation is a fine line. Look at one of the criteria that Ireland ran afoul of: "the basis of profit determination for companies in a multinational group departs from internationally accepted rules"
Which of course is amusing because there aren't really any internationally accepted rules. Companies like Apple e.g. Ikea, Coke, Google etc all do this and many countries allow it in particular the US.
I think it's fantastic that this precedent has been set. But it is a precedent none the less.
But low tax rates are not "state aid", "aid" is an English word meaning giving something to somebody. "Tax" means the opposite: taking it away.
The EU Commission is now engaged in a rather grotesque power grab in which despite having no mandate to interfere with member tax policies they are attempting to gain control anyway, without treaty change, by redefining low tax rates as a kind of subsidy.
There is no real precedent for this kind of legal abuse - to claim Apple should have anticipated it is absurd.
EU has held for almost two decades that "an effective level of taxation which is significantly lower than the general level of taxation in the country concerned" constitutes "harmful tax competition". The most logical way to undo such unfair benefit is to rule the company to return the unfair benefit it gained with interest. I don't see anything but a welcome measure to level the field for competition.
There definitely is now though and you can be sure legal teams around the world will be advising senior leadership teams to rearrange their corporate structures accordingly.