Because Ireland has joined the EU and knowingly chosen to participate in treaties pertaining to the shared market. If Ireland wanted to leave the EU then it would be free to do so, then it can cut Apple all the tax breaks it wants. However as is, Ireland is trying to please two masters at the same time and the court cases seem pretty clear about how that is going for them.
Apple willingly sold in the eu then found loopholes to save on tax. They created shell corporratioms to save on tax yeah Apple is correct and Ireland is only one in the wrong.
